docs/formatdomain.html.in | 40 ++- docs/schemas/domaincommon.rng | 17 + po/POTFILES.in | 1 + src/Makefile.am | 1 + src/conf/domain_conf.c | 81 ++++- src/conf/domain_conf.h | 10 + src/libvirt_private.syms | 19 ++ src/qemu/qemu_cgroup.c | 35 ++ src/qemu/qemu_command.c | 49 +++ src/qemu/qemu_command.h | 5 + src/qemu/qemu_domain.c | 13 + src/qemu/qemu_domain_address.c | 12 +- src/qemu/qemu_hostdev.c | 37 ++ src/qemu/qemu_hostdev.h | 8 + src/qemu/qemu_hotplug.c | 2 + src/security/security_apparmor.c | 3 + src/security/security_dac.c | 56 +++ src/security/security_selinux.c | 55 +++ src/util/virhostdev.c | 179 +++++++++- src/util/virhostdev.h | 16 + src/util/virmdev.c | 375 +++++++++++++++++++++ src/util/virmdev.h | 85 +++++ tests/domaincapsschemadata/full.xml | 1 + ...qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml | 37 ++ .../qemuxml2argv-hostdev-mdev-unmanaged.args | 25 ++ .../qemuxml2argv-hostdev-mdev-unmanaged.xml | 38 +++ tests/qemuxml2argvtest.c | 6 + .../qemuxml2xmlout-hostdev-mdev-unmanaged.xml | 41 +++ tests/qemuxml2xmltest.c | 1 + 29 files changed, 1239 insertions(+), 9 deletions(-) create mode 100644 src/util/virmdev.c create mode 100644 src/util/virmdev.h create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.args create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.xml create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-hostdev-mdev-unmanaged.xml
Finally. It's here. This is the initial suggestion on how libvirt might interract with the mdev framework, currently only focussing on the non-managed devices, i.e. those pre-created by the user, since that will be revisited once we all settled on how the XML should look like, given we might not want to use the sysfs path directly as an attribute in the domain XML. My proposal on the XML is the following: <hostdev mode='subsystem' type='mdev'> <source> <!-- this is the host's physical device address --> <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> <uuid>vGPU_UUID<uuid> <source> <!-- target PCI address can be omitted to assign it automatically --> </hostdev> So the mediated device is identified by the physical parent device visible on the host and a UUID which allows us to construct the sysfs path by ourselves, which we then put on the QEMU's command line. A few remarks if you actually happen to have a machine to test this on: - right now the mediated devices are one-time use only, i.e. they have to be recreated before every machine boot - I wouldn't recommend assigning multiple vGPUs to a single domain Once this series is sorted out, we can then continue with 'managed=yes' where as Laine pointed out [1], we need to figure out how exactly should the management layer hint libvirt which vGPU type should be used for device instantiation. [1] https://www.redhat.com/archives/libvir-list/2017-January/msg00287.html #pleaseshareyourfeedback Thanks, Erik Erik Skultety (16): util: Introduce new module virmdev conf: Introduce new hostdev device type mdev docs: Update RNG schema to reflect the new hostdev type mdev conf: Adjust the domain parser to work with mdevs Adjust the formatter to reflect the new hostdev type mdev security: dac: Enable labeling of vfio mediated devices security: selinux: Enable labeling of vfio mediated devices conf: Enable cold-plug of a mediated device qemu: Assign PCI addresses for mediated devices as well hostdev: Maintain a driver list of active mediated devices hostdev: Introduce a reattach method for mediated devices qemu: cgroup: Adjust cgroups' logic to allow mediated devices qemu: namespace: Hook up the discovery of mdevs into the namespace code qemu: Format mdevs on the qemu command line test: Add some test cases for our test suite regarding the mdevs docs: Document the new hostdev device type 'mdev' docs/formatdomain.html.in | 40 ++- docs/schemas/domaincommon.rng | 17 + po/POTFILES.in | 1 + src/Makefile.am | 1 + src/conf/domain_conf.c | 81 ++++- src/conf/domain_conf.h | 10 + src/libvirt_private.syms | 19 ++ src/qemu/qemu_cgroup.c | 35 ++ src/qemu/qemu_command.c | 49 +++ src/qemu/qemu_command.h | 5 + src/qemu/qemu_domain.c | 13 + src/qemu/qemu_domain_address.c | 12 +- src/qemu/qemu_hostdev.c | 37 ++ src/qemu/qemu_hostdev.h | 8 + src/qemu/qemu_hotplug.c | 2 + src/security/security_apparmor.c | 3 + src/security/security_dac.c | 56 +++ src/security/security_selinux.c | 55 +++ src/util/virhostdev.c | 179 +++++++++- src/util/virhostdev.h | 16 + src/util/virmdev.c | 375 +++++++++++++++++++++ src/util/virmdev.h | 85 +++++ tests/domaincapsschemadata/full.xml | 1 + ...qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml | 37 ++ .../qemuxml2argv-hostdev-mdev-unmanaged.args | 25 ++ .../qemuxml2argv-hostdev-mdev-unmanaged.xml | 38 +++ tests/qemuxml2argvtest.c | 6 + .../qemuxml2xmlout-hostdev-mdev-unmanaged.xml | 41 +++ tests/qemuxml2xmltest.c | 1 + 29 files changed, 1239 insertions(+), 9 deletions(-) create mode 100644 src/util/virmdev.c create mode 100644 src/util/virmdev.h create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.args create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.xml create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-hostdev-mdev-unmanaged.xml -- 2.10.2 -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On 06.02.2017 13:19, Erik Skultety wrote: > Finally. It's here. This is the initial suggestion on how libvirt might > interract with the mdev framework, currently only focussing on the non-managed > devices, i.e. those pre-created by the user, since that will be revisited once > we all settled on how the XML should look like, given we might not want to use > the sysfs path directly as an attribute in the domain XML. My proposal on the > XML is the following: > > <hostdev mode='subsystem' type='mdev'> > <source> > <!-- this is the host's physical device address --> > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > <uuid>vGPU_UUID<uuid> > <source> > <!-- target PCI address can be omitted to assign it automatically --> > </hostdev> > > So the mediated device is identified by the physical parent device visible on > the host and a UUID which allows us to construct the sysfs path by ourselves, > which we then put on the QEMU's command line. > > A few remarks if you actually happen to have a machine to test this on: > - right now the mediated devices are one-time use only, i.e. they have to be > recreated before every machine boot > - I wouldn't recommend assigning multiple vGPUs to a single domain > > Once this series is sorted out, we can then continue with 'managed=yes' where > as Laine pointed out [1], we need to figure out how exactly should the > management layer hint libvirt which vGPU type should be used for device > instantiation. > > [1] https://www.redhat.com/archives/libvir-list/2017-January/msg00287.html > > #pleaseshareyourfeedback > > Thanks, > Erik > > Erik Skultety (16): > util: Introduce new module virmdev > conf: Introduce new hostdev device type mdev > docs: Update RNG schema to reflect the new hostdev type mdev > conf: Adjust the domain parser to work with mdevs > Adjust the formatter to reflect the new hostdev type mdev > security: dac: Enable labeling of vfio mediated devices > security: selinux: Enable labeling of vfio mediated devices > conf: Enable cold-plug of a mediated device > qemu: Assign PCI addresses for mediated devices as well > hostdev: Maintain a driver list of active mediated devices > hostdev: Introduce a reattach method for mediated devices > qemu: cgroup: Adjust cgroups' logic to allow mediated devices > qemu: namespace: Hook up the discovery of mdevs into the namespace > code > qemu: Format mdevs on the qemu command line > test: Add some test cases for our test suite regarding the mdevs > docs: Document the new hostdev device type 'mdev' > > docs/formatdomain.html.in | 40 ++- > docs/schemas/domaincommon.rng | 17 + > po/POTFILES.in | 1 + > src/Makefile.am | 1 + > src/conf/domain_conf.c | 81 ++++- > src/conf/domain_conf.h | 10 + > src/libvirt_private.syms | 19 ++ > src/qemu/qemu_cgroup.c | 35 ++ > src/qemu/qemu_command.c | 49 +++ > src/qemu/qemu_command.h | 5 + > src/qemu/qemu_domain.c | 13 + > src/qemu/qemu_domain_address.c | 12 +- > src/qemu/qemu_hostdev.c | 37 ++ > src/qemu/qemu_hostdev.h | 8 + > src/qemu/qemu_hotplug.c | 2 + > src/security/security_apparmor.c | 3 + > src/security/security_dac.c | 56 +++ > src/security/security_selinux.c | 55 +++ > src/util/virhostdev.c | 179 +++++++++- > src/util/virhostdev.h | 16 + > src/util/virmdev.c | 375 +++++++++++++++++++++ > src/util/virmdev.h | 85 +++++ > tests/domaincapsschemadata/full.xml | 1 + > ...qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml | 37 ++ > .../qemuxml2argv-hostdev-mdev-unmanaged.args | 25 ++ > .../qemuxml2argv-hostdev-mdev-unmanaged.xml | 38 +++ > tests/qemuxml2argvtest.c | 6 + > .../qemuxml2xmlout-hostdev-mdev-unmanaged.xml | 41 +++ > tests/qemuxml2xmltest.c | 1 + > 29 files changed, 1239 insertions(+), 9 deletions(-) > create mode 100644 src/util/virmdev.c > create mode 100644 src/util/virmdev.h > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.args > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.xml > create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-hostdev-mdev-unmanaged.xml > I'm no expert in mdevs, but from code POV these look solid. Michal -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Mon, 6 Feb 2017 13:19:42 +0100 Erik Skultety <eskultet@redhat.com> wrote: > Finally. It's here. This is the initial suggestion on how libvirt might > interract with the mdev framework, currently only focussing on the non-managed > devices, i.e. those pre-created by the user, since that will be revisited once > we all settled on how the XML should look like, given we might not want to use > the sysfs path directly as an attribute in the domain XML. My proposal on the > XML is the following: > > <hostdev mode='subsystem' type='mdev'> > <source> > <!-- this is the host's physical device address --> > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > <uuid>vGPU_UUID<uuid> > <source> > <!-- target PCI address can be omitted to assign it automatically --> > </hostdev> > > So the mediated device is identified by the physical parent device visible on > the host and a UUID which allows us to construct the sysfs path by ourselves, > which we then put on the QEMU's command line. Based on your test code, I think you're creating something like this: -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc That would explain the need for the parent device address, but that's an entirely self inflicted requirement. For a managed="no" scenarios, we shouldn't need the parent, we can get to the mdev device via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it seems that the UUID should be the only required source element for managed="no". For managed="yes", it seems like the parent device is still an optional field. The most important thing that libvirt needs to know when creating a mdev device for a VM is the mdev type name. The parent device should be an optional field to help higher level management tools deal with placement of the device for locality or load balancing. Also, we can't assume that the parent device is a PCI device, the sample mtty driver already breaks this assumption. Also, grep'ing through the patches, I don't see that the "device_api" file is being used to test that the mdev device actually exports the vfio-pci API before making use of it with the QEMU vfio-pci driver. We don't yet have any examples to the contrary, but non vfio-pci mdev devices are in development. Just like we can't assume the parent device type, we can't assume the API of an mdev device to the user. Thanks, Alex > A few remarks if you actually happen to have a machine to test this on: > - right now the mediated devices are one-time use only, i.e. they have to be > recreated before every machine boot > - I wouldn't recommend assigning multiple vGPUs to a single domain > > Once this series is sorted out, we can then continue with 'managed=yes' where > as Laine pointed out [1], we need to figure out how exactly should the > management layer hint libvirt which vGPU type should be used for device > instantiation. > > [1] https://www.redhat.com/archives/libvir-list/2017-January/msg00287.html > > #pleaseshareyourfeedback > > Thanks, > Erik > > Erik Skultety (16): > util: Introduce new module virmdev > conf: Introduce new hostdev device type mdev > docs: Update RNG schema to reflect the new hostdev type mdev > conf: Adjust the domain parser to work with mdevs > Adjust the formatter to reflect the new hostdev type mdev > security: dac: Enable labeling of vfio mediated devices > security: selinux: Enable labeling of vfio mediated devices > conf: Enable cold-plug of a mediated device > qemu: Assign PCI addresses for mediated devices as well > hostdev: Maintain a driver list of active mediated devices > hostdev: Introduce a reattach method for mediated devices > qemu: cgroup: Adjust cgroups' logic to allow mediated devices > qemu: namespace: Hook up the discovery of mdevs into the namespace > code > qemu: Format mdevs on the qemu command line > test: Add some test cases for our test suite regarding the mdevs > docs: Document the new hostdev device type 'mdev' > > docs/formatdomain.html.in | 40 ++- > docs/schemas/domaincommon.rng | 17 + > po/POTFILES.in | 1 + > src/Makefile.am | 1 + > src/conf/domain_conf.c | 81 ++++- > src/conf/domain_conf.h | 10 + > src/libvirt_private.syms | 19 ++ > src/qemu/qemu_cgroup.c | 35 ++ > src/qemu/qemu_command.c | 49 +++ > src/qemu/qemu_command.h | 5 + > src/qemu/qemu_domain.c | 13 + > src/qemu/qemu_domain_address.c | 12 +- > src/qemu/qemu_hostdev.c | 37 ++ > src/qemu/qemu_hostdev.h | 8 + > src/qemu/qemu_hotplug.c | 2 + > src/security/security_apparmor.c | 3 + > src/security/security_dac.c | 56 +++ > src/security/security_selinux.c | 55 +++ > src/util/virhostdev.c | 179 +++++++++- > src/util/virhostdev.h | 16 + > src/util/virmdev.c | 375 +++++++++++++++++++++ > src/util/virmdev.h | 85 +++++ > tests/domaincapsschemadata/full.xml | 1 + > ...qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml | 37 ++ > .../qemuxml2argv-hostdev-mdev-unmanaged.args | 25 ++ > .../qemuxml2argv-hostdev-mdev-unmanaged.xml | 38 +++ > tests/qemuxml2argvtest.c | 6 + > .../qemuxml2xmlout-hostdev-mdev-unmanaged.xml | 41 +++ > tests/qemuxml2xmltest.c | 1 + > 29 files changed, 1239 insertions(+), 9 deletions(-) > create mode 100644 src/util/virmdev.c > create mode 100644 src/util/virmdev.h > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged-no-uuid.xml > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.args > create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-hostdev-mdev-unmanaged.xml > create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-hostdev-mdev-unmanaged.xml > -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: > On Mon, 6 Feb 2017 13:19:42 +0100 > Erik Skultety <eskultet@redhat.com> wrote: > > > Finally. It's here. This is the initial suggestion on how libvirt might > > interract with the mdev framework, currently only focussing on the non-managed > > devices, i.e. those pre-created by the user, since that will be revisited once > > we all settled on how the XML should look like, given we might not want to use > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > XML is the following: > > > > <hostdev mode='subsystem' type='mdev'> > > <source> > > <!-- this is the host's physical device address --> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > <uuid>vGPU_UUID<uuid> > > <source> > > <!-- target PCI address can be omitted to assign it automatically --> > > </hostdev> > > > > So the mediated device is identified by the physical parent device visible on > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > which we then put on the QEMU's command line. > > Based on your test code, I think you're creating something like this: > > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc > > That would explain the need for the parent device address, but that's > an entirely self inflicted requirement. For a managed="no" scenarios, > we shouldn't need the parent, we can get to the mdev device > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it True, for managed="no" would this path be a nice optimization. > seems that the UUID should be the only required source element for > managed="no". > > For managed="yes", it seems like the parent device is still an optional The reason I went with the parent address element (and purposely neglecting the sample mtty driver) was that I assumed any modern mdev capable HW would be accessible through the PCI bus on the host. Also I wanted to explicitly hint libvirt as much as possible which parent device a vGPU device instance should be created on in case there are more than one of them, rather then scanning sysfs for a suitable parent which actually supports the given vGPU type. > field. The most important thing that libvirt needs to know when > creating a mdev device for a VM is the mdev type name. The parent > device should be an optional field to help higher level management > tools deal with placement of the device for locality or load balancing. > Also, we can't assume that the parent device is a PCI device, the > sample mtty driver already breaks this assumption. Since we need to assume non-PCI devices and we still need to enable management to hint libvirt about the parent to utilize load balancing and stuff, I've come up with the following adjustments/ideas on how to reflect that in the XML: - still use the address element but use it with the 'type' attribute [1] (still breaks the sample mtty driver though) while making the element truly optional if I'm going to be outvoted in favor of scanning the directory for a suitable parent device on our own, rather than requiring the user to provide that - providing either an attribute or a standalone element for the parent device name, like a string version of the PCI address or whatever form the parent device comes in (doesn't break the mtty driver but I don't quite like this) - providing a path element/attribute to sysfs pointing to the parent device which I'm afraid is what Daniel is not in favor of libvirt doing So, this is what I've so far come up with in terms of hinting libvirt about the parent device, do you have any input on this, maybe some more ideas on how we should identify the parent device? > > Also, grep'ing through the patches, I don't see that the "device_api" Yep, this was also on purpose since as you write below, right now the only functioning mdev devices we have to work with are vfio-pci capable only, so with this RFC I wanted to gather some feedback on whether I'm moving the right direction in the first place. So yeah, I thought this could be added at any point later. [1] http://libvirt.org/formatdomain.html#elementsAddress Erik > file is being used to test that the mdev device actually exports the > vfio-pci API before making use of it with the QEMU vfio-pci driver. We > don't yet have any examples to the contrary, but non vfio-pci mdev > devices are in development. Just like we can't assume the parent > device type, we can't assume the API of an mdev device to the user. > Thanks, > > Alex > > > A few remarks if you actually happen to have a machine to test this on: > > - right now the mediated devices are one-time use only, i.e. they have to be > > recreated before every machine boot > > - I wouldn't recommend assigning multiple vGPUs to a single domain > > > > Once this series is sorted out, we can then continue with 'managed=yes' where > > as Laine pointed out [1], we need to figure out how exactly should the > > management layer hint libvirt which vGPU type should be used for device > > instantiation. > > > > [1] https://www.redhat.com/archives/libvir-list/2017-January/msg00287.html > > -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Tue, 7 Feb 2017 17:26:51 +0100 Erik Skultety <eskultet@redhat.com> wrote: > On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: > > On Mon, 6 Feb 2017 13:19:42 +0100 > > Erik Skultety <eskultet@redhat.com> wrote: > > > > > Finally. It's here. This is the initial suggestion on how libvirt might > > > interract with the mdev framework, currently only focussing on the non-managed > > > devices, i.e. those pre-created by the user, since that will be revisited once > > > we all settled on how the XML should look like, given we might not want to use > > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > > XML is the following: > > > > > > <hostdev mode='subsystem' type='mdev'> > > > <source> > > > <!-- this is the host's physical device address --> > > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > > <uuid>vGPU_UUID<uuid> > > > <source> > > > <!-- target PCI address can be omitted to assign it automatically --> > > > </hostdev> > > > > > > So the mediated device is identified by the physical parent device visible on > > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > > which we then put on the QEMU's command line. > > > > Based on your test code, I think you're creating something like this: > > > > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc > > > > That would explain the need for the parent device address, but that's > > an entirely self inflicted requirement. For a managed="no" scenarios, > > we shouldn't need the parent, we can get to the mdev device > > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it > > True, for managed="no" would this path be a nice optimization. > > > seems that the UUID should be the only required source element for > > managed="no". > > > > For managed="yes", it seems like the parent device is still an optional > > The reason I went with the parent address element (and purposely neglecting the > sample mtty driver) was that I assumed any modern mdev capable HW would be > accessible through the PCI bus on the host. Also I wanted to explicitly hint > libvirt as much as possible which parent device a vGPU device instance should > be created on in case there are more than one of them, rather then scanning > sysfs for a suitable parent which actually supports the given vGPU type. > > > field. The most important thing that libvirt needs to know when > > creating a mdev device for a VM is the mdev type name. The parent > > device should be an optional field to help higher level management > > tools deal with placement of the device for locality or load balancing. > > Also, we can't assume that the parent device is a PCI device, the > > sample mtty driver already breaks this assumption. > > Since we need to assume non-PCI devices and we still need to enable management > to hint libvirt about the parent to utilize load balancing and stuff, I've come > up with the following adjustments/ideas on how to reflect that in the XML: > - still use the address element but use it with the 'type' attribute [1] (still > breaks the sample mtty driver though) while making the element truly optional > if I'm going to be outvoted in favor of scanning the directory for a suitable > parent device on our own, rather than requiring the user to provide that > > - providing either an attribute or a standalone element for the parent device > name, like a string version of the PCI address or whatever form the parent > device comes in (doesn't break the mtty driver but I don't quite like this) > > - providing a path element/attribute to sysfs pointing to the parent device > which I'm afraid is what Daniel is not in favor of libvirt doing > > So, this is what I've so far come up with in terms of hinting libvirt about the > parent device, do you have any input on this, maybe some more ideas on how we > should identify the parent device? IMO, if we cannot account for the mtty sample driver, we're doing it wrong. I suppose we can leave it unspecified how one selects a parent device for the mtty driver, but it should be possible to expand the syntax to include it. So I think that means that when the parent address is provided, the parent address type needs to be specified as PCI. So... <hostdev mode='subsystem' type='mdev'> This needs to encompass the device API or else the optional VM address cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to how we specify the device type for PCI controllers where we have multiple options: <hostdev mode='subsystem' type='mdev' model='vfio-pci'> <source> For managed='no', I don't see that anything other than the mdev UUID is useful. <uuid>MDEV_UUID</uuid> If libvirt gets into the business of creating mdev devices and we call that managed='yes', then the mdev type to create is required. I don't know whether there's anything similar we can steal syntax from: <type>"nvidia-11"</type> That's pretty horrible, needs some xml guru love. We need to provide for specifying a parent, but we can't assume the type and address format of the parent. If we say the parent is a string, then we don't care, libvirt simply matches the /sys/clas/mdev_bus/$STRING/ device. If we want libvirt to interpret the parent address (I can't figure what value this adds, but aiui raw strings are frowned upon), then the address type would need to be specified. So instead of: <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> Perhaps: <address type='pci' domain='0x0000' bus='0x00'...> If we want to support mtty here, we'd need a different type, but at least we have the possibility to define that (though if parent is simply a string then even mtty works). <source> The type of the optional <address> here would be based on the "model" of the hostdev. </hostdev> Clearly I'm less than a novice at defining xml tags, this is just what I think needs to be there. > > Also, grep'ing through the patches, I don't see that the "device_api" > > Yep, this was also on purpose since as you write below, right now the only > functioning mdev devices we have to work with are vfio-pci capable only, so > with this RFC I wanted to gather some feedback on whether I'm moving the right > direction in the first place. So yeah, I thought this could be added at any point > later. Hmm, I think that might be painting us into a corner for the future. > [1] http://libvirt.org/formatdomain.html#elementsAddress I see here that we already do the <address type='pci'...> thing, so using that as the parent source element fits. The VM <address> though is optional, so we can't rely on queues from that to tell us what mdev type to expect, which implies we do need something like the model='vfio-pci' to determine the VM address format. Thanks, Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On 07/02/17 12:29 -0700, Alex Williamson wrote: >On Tue, 7 Feb 2017 17:26:51 +0100 >Erik Skultety <eskultet@redhat.com> wrote: > >> On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: >> > On Mon, 6 Feb 2017 13:19:42 +0100 >> > Erik Skultety <eskultet@redhat.com> wrote: >> > >> > > Finally. It's here. This is the initial suggestion on how libvirt might >> > > interract with the mdev framework, currently only focussing on the non-managed >> > > devices, i.e. those pre-created by the user, since that will be revisited once >> > > we all settled on how the XML should look like, given we might not want to use >> > > the sysfs path directly as an attribute in the domain XML. My proposal on the >> > > XML is the following: >> > > >> > > <hostdev mode='subsystem' type='mdev'> >> > > <source> >> > > <!-- this is the host's physical device address --> >> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> >> > > <uuid>vGPU_UUID<uuid> >> > > <source> >> > > <!-- target PCI address can be omitted to assign it automatically --> >> > > </hostdev> >> > > >> > > So the mediated device is identified by the physical parent device visible on >> > > the host and a UUID which allows us to construct the sysfs path by ourselves, >> > > which we then put on the QEMU's command line. >> > >> > Based on your test code, I think you're creating something like this: >> > >> > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc >> > >> > That would explain the need for the parent device address, but that's >> > an entirely self inflicted requirement. For a managed="no" scenarios, >> > we shouldn't need the parent, we can get to the mdev device >> > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it >> >> True, for managed="no" would this path be a nice optimization. >> >> > seems that the UUID should be the only required source element for >> > managed="no". >> > >> > For managed="yes", it seems like the parent device is still an optional >> >> The reason I went with the parent address element (and purposely neglecting the >> sample mtty driver) was that I assumed any modern mdev capable HW would be >> accessible through the PCI bus on the host. Also I wanted to explicitly hint >> libvirt as much as possible which parent device a vGPU device instance should >> be created on in case there are more than one of them, rather then scanning >> sysfs for a suitable parent which actually supports the given vGPU type. >> >> > field. The most important thing that libvirt needs to know when >> > creating a mdev device for a VM is the mdev type name. The parent >> > device should be an optional field to help higher level management >> > tools deal with placement of the device for locality or load balancing. >> > Also, we can't assume that the parent device is a PCI device, the >> > sample mtty driver already breaks this assumption. >> >> Since we need to assume non-PCI devices and we still need to enable management >> to hint libvirt about the parent to utilize load balancing and stuff, I've come >> up with the following adjustments/ideas on how to reflect that in the XML: >> - still use the address element but use it with the 'type' attribute [1] (still >> breaks the sample mtty driver though) while making the element truly optional >> if I'm going to be outvoted in favor of scanning the directory for a suitable >> parent device on our own, rather than requiring the user to provide that >> >> - providing either an attribute or a standalone element for the parent device >> name, like a string version of the PCI address or whatever form the parent >> device comes in (doesn't break the mtty driver but I don't quite like this) >> >> - providing a path element/attribute to sysfs pointing to the parent device >> which I'm afraid is what Daniel is not in favor of libvirt doing >> >> So, this is what I've so far come up with in terms of hinting libvirt about the >> parent device, do you have any input on this, maybe some more ideas on how we >> should identify the parent device? > >IMO, if we cannot account for the mtty sample driver, we're doing it >wrong. I suppose we can leave it unspecified how one selects a parent >device for the mtty driver, but it should be possible to expand the >syntax to include it. So I think that means that when the parent >address is provided, the parent address type needs to be specified as >PCI. So... > > <hostdev mode='subsystem' type='mdev'> > >This needs to encompass the device API or else the optional VM address >cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to >how we specify the device type for PCI controllers where we have >multiple options: > > <hostdev mode='subsystem' type='mdev' model='vfio-pci'> > > <source> > >For managed='no', I don't see that anything other than the mdev UUID is >useful. > > <uuid>MDEV_UUID</uuid> > >If libvirt gets into the business of creating mdev devices and we call >that managed='yes', then the mdev type to create is required. I don't >know whether there's anything similar we can steal syntax from: > > <type>"nvidia-11"</type> > >That's pretty horrible, needs some xml guru love. > >We need to provide for specifying a parent, but we can't assume the >From higher level perspective, I believe it would be "good enough" for most of the cases to only specify the type. Libvirt will anyway have to be able to enumerate the devices for listAllDevices afaik. My wish would be specifying <hostdev mode='subsystem' type='mdev'> <type>nvidia-11</type> </hostdev> unless the user has specific requests or some other decision (mmio numa placement) takes place. We would additionally need (allocated instances/max instances of that type) in listAllDevices to account for the specific assignment possibility. I'm not sure what the decision was wrt type naming, can 2 different cards have similarly named type with different meaning? Sorry if I've missed some obvious reason why this can't work. mpolednik >type and address format of the parent. If we say the parent is a >string, then we don't care, libvirt simply matches >the /sys/clas/mdev_bus/$STRING/ device. If we want libvirt to >interpret the parent address (I can't figure what value this adds, but >aiui raw strings are frowned upon), then the address type would need to >be specified. So instead of: > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > >Perhaps: > > <address type='pci' domain='0x0000' bus='0x00'...> > >If we want to support mtty here, we'd need a different type, but at >least we have the possibility to define that (though if parent is >simply a string then even mtty works). > > <source> > >The type of the optional <address> here would be based on the "model" >of the hostdev. > > </hostdev> > >Clearly I'm less than a novice at defining xml tags, this is just what >I think needs to be there. > >> > Also, grep'ing through the patches, I don't see that the "device_api" >> >> Yep, this was also on purpose since as you write below, right now the only >> functioning mdev devices we have to work with are vfio-pci capable only, so >> with this RFC I wanted to gather some feedback on whether I'm moving the right >> direction in the first place. So yeah, I thought this could be added at any point >> later. > >Hmm, I think that might be painting us into a corner for the future. > >> [1] http://libvirt.org/formatdomain.html#elementsAddress > >I see here that we already do the <address type='pci'...> thing, so >using that as the parent source element fits. > >The VM <address> though is optional, so we can't rely on queues from >that to tell us what mdev type to expect, which implies we do need >something like the model='vfio-pci' to determine the VM address format. >Thanks, > >Alex > >-- >libvir-list mailing list >libvir-list@redhat.com >https://www.redhat.com/mailman/listinfo/libvir-list -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Tue, 14 Feb 2017 16:50:14 +0100 Martin Polednik <mpolednik@redhat.com> wrote: > On 07/02/17 12:29 -0700, Alex Williamson wrote: > >On Tue, 7 Feb 2017 17:26:51 +0100 > >Erik Skultety <eskultet@redhat.com> wrote: > > > >> On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: > >> > On Mon, 6 Feb 2017 13:19:42 +0100 > >> > Erik Skultety <eskultet@redhat.com> wrote: > >> > > >> > > Finally. It's here. This is the initial suggestion on how libvirt might > >> > > interract with the mdev framework, currently only focussing on the non-managed > >> > > devices, i.e. those pre-created by the user, since that will be revisited once > >> > > we all settled on how the XML should look like, given we might not want to use > >> > > the sysfs path directly as an attribute in the domain XML. My proposal on the > >> > > XML is the following: > >> > > > >> > > <hostdev mode='subsystem' type='mdev'> > >> > > <source> > >> > > <!-- this is the host's physical device address --> > >> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > >> > > <uuid>vGPU_UUID<uuid> > >> > > <source> > >> > > <!-- target PCI address can be omitted to assign it automatically --> > >> > > </hostdev> > >> > > > >> > > So the mediated device is identified by the physical parent device visible on > >> > > the host and a UUID which allows us to construct the sysfs path by ourselves, > >> > > which we then put on the QEMU's command line. > >> > > >> > Based on your test code, I think you're creating something like this: > >> > > >> > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc > >> > > >> > That would explain the need for the parent device address, but that's > >> > an entirely self inflicted requirement. For a managed="no" scenarios, > >> > we shouldn't need the parent, we can get to the mdev device > >> > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it > >> > >> True, for managed="no" would this path be a nice optimization. > >> > >> > seems that the UUID should be the only required source element for > >> > managed="no". > >> > > >> > For managed="yes", it seems like the parent device is still an optional > >> > >> The reason I went with the parent address element (and purposely neglecting the > >> sample mtty driver) was that I assumed any modern mdev capable HW would be > >> accessible through the PCI bus on the host. Also I wanted to explicitly hint > >> libvirt as much as possible which parent device a vGPU device instance should > >> be created on in case there are more than one of them, rather then scanning > >> sysfs for a suitable parent which actually supports the given vGPU type. > >> > >> > field. The most important thing that libvirt needs to know when > >> > creating a mdev device for a VM is the mdev type name. The parent > >> > device should be an optional field to help higher level management > >> > tools deal with placement of the device for locality or load balancing. > >> > Also, we can't assume that the parent device is a PCI device, the > >> > sample mtty driver already breaks this assumption. > >> > >> Since we need to assume non-PCI devices and we still need to enable management > >> to hint libvirt about the parent to utilize load balancing and stuff, I've come > >> up with the following adjustments/ideas on how to reflect that in the XML: > >> - still use the address element but use it with the 'type' attribute [1] (still > >> breaks the sample mtty driver though) while making the element truly optional > >> if I'm going to be outvoted in favor of scanning the directory for a suitable > >> parent device on our own, rather than requiring the user to provide that > >> > >> - providing either an attribute or a standalone element for the parent device > >> name, like a string version of the PCI address or whatever form the parent > >> device comes in (doesn't break the mtty driver but I don't quite like this) > >> > >> - providing a path element/attribute to sysfs pointing to the parent device > >> which I'm afraid is what Daniel is not in favor of libvirt doing > >> > >> So, this is what I've so far come up with in terms of hinting libvirt about the > >> parent device, do you have any input on this, maybe some more ideas on how we > >> should identify the parent device? > > > >IMO, if we cannot account for the mtty sample driver, we're doing it > >wrong. I suppose we can leave it unspecified how one selects a parent > >device for the mtty driver, but it should be possible to expand the > >syntax to include it. So I think that means that when the parent > >address is provided, the parent address type needs to be specified as > >PCI. So... > > > > <hostdev mode='subsystem' type='mdev'> > > > >This needs to encompass the device API or else the optional VM address > >cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to > >how we specify the device type for PCI controllers where we have > >multiple options: > > > > <hostdev mode='subsystem' type='mdev' model='vfio-pci'> > > > > <source> > > > >For managed='no', I don't see that anything other than the mdev UUID is > >useful. > > > > <uuid>MDEV_UUID</uuid> > > > >If libvirt gets into the business of creating mdev devices and we call > >that managed='yes', then the mdev type to create is required. I don't > >know whether there's anything similar we can steal syntax from: > > > > <type>"nvidia-11"</type> > > > >That's pretty horrible, needs some xml guru love. > > > >We need to provide for specifying a parent, but we can't assume the > > From higher level perspective, I believe it would be "good > enough" for most of the cases to only specify the type. Libvirt will > anyway have to be able to enumerate the devices for listAllDevices > afaik. > > My wish would be specifying > <hostdev mode='subsystem' type='mdev'> > <type>nvidia-11</type> > </hostdev> > unless the user has specific requests or some other decision (mmio > numa placement) takes place. Yes, the <type> is the minimum information necessary for libvirt to create the mdev device itself. A <source> section could add optional placement information. Note though that without an nvidia-11 type device on the system to query, the xml doesn't tell us what sort of device this creates in the VM. We could assume that it's vfio-pci, but designing in an assumption isn't a great idea. So, as above, some mechanism to make the xml self contained, such as specifying the model as vfio-pci, helps avoid that assumption and allows us to know the format for expressing the VM <address> > We would additionally need (allocated instances/max instances of that > type) in listAllDevices to account for the specific assignment > possibility. mdev devices support an available_instances per mdev type that is dynamically updated as devices are created. The interaction of available_instances between different types is going to require some heuristics to understand. Some vendors may not support heterogeneous types, others may pull from a common pool of resources, where each type may consume resources from that pool at different rates. > I'm not sure what the decision was wrt type naming, can 2 different > cards have similarly named type with different meaning? We don't deal in similarities, each type ID is unique and it's up to the mdev vendor driver to make sure that an "nvidia-11" on and M60 card is software equivalent to an "nvidia-11" on an M10 card. If they're not equivalent, the type ID will be different. Something we may want to consider eventually is whether we want/need to deal with compatibility strings. For instance, NVIDIA seems to be tying the type ID strongly to specific implementations, an nvidia-11 may only be available on an M60 card. An M10 card may offer an nvidia-21 type with similar capabilities. There may be a need to express an mdev device as compatible with various type IDs for hardware availability, at the risk of exposing slight variations to the VM. This could also make placement easier for vendor drivers that only support homogeneous mdev devices, "I prefer an mdev ID of type 'nvidia-11', but will accept one of type 'nvidia-12,nvidia-21'". Thanks, Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On 14/02/17 09:58 -0700, Alex Williamson wrote: >On Tue, 14 Feb 2017 16:50:14 +0100 >Martin Polednik <mpolednik@redhat.com> wrote: > >> On 07/02/17 12:29 -0700, Alex Williamson wrote: >> >On Tue, 7 Feb 2017 17:26:51 +0100 >> >Erik Skultety <eskultet@redhat.com> wrote: >> > >> >> On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: >> >> > On Mon, 6 Feb 2017 13:19:42 +0100 >> >> > Erik Skultety <eskultet@redhat.com> wrote: >> >> > >> >> > > Finally. It's here. This is the initial suggestion on how libvirt might >> >> > > interract with the mdev framework, currently only focussing on the non-managed >> >> > > devices, i.e. those pre-created by the user, since that will be revisited once >> >> > > we all settled on how the XML should look like, given we might not want to use >> >> > > the sysfs path directly as an attribute in the domain XML. My proposal on the >> >> > > XML is the following: >> >> > > >> >> > > <hostdev mode='subsystem' type='mdev'> >> >> > > <source> >> >> > > <!-- this is the host's physical device address --> >> >> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> >> >> > > <uuid>vGPU_UUID<uuid> >> >> > > <source> >> >> > > <!-- target PCI address can be omitted to assign it automatically --> >> >> > > </hostdev> >> >> > > >> >> > > So the mediated device is identified by the physical parent device visible on >> >> > > the host and a UUID which allows us to construct the sysfs path by ourselves, >> >> > > which we then put on the QEMU's command line. >> >> > >> >> > Based on your test code, I think you're creating something like this: >> >> > >> >> > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc >> >> > >> >> > That would explain the need for the parent device address, but that's >> >> > an entirely self inflicted requirement. For a managed="no" scenarios, >> >> > we shouldn't need the parent, we can get to the mdev device >> >> > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it >> >> >> >> True, for managed="no" would this path be a nice optimization. >> >> >> >> > seems that the UUID should be the only required source element for >> >> > managed="no". >> >> > >> >> > For managed="yes", it seems like the parent device is still an optional >> >> >> >> The reason I went with the parent address element (and purposely neglecting the >> >> sample mtty driver) was that I assumed any modern mdev capable HW would be >> >> accessible through the PCI bus on the host. Also I wanted to explicitly hint >> >> libvirt as much as possible which parent device a vGPU device instance should >> >> be created on in case there are more than one of them, rather then scanning >> >> sysfs for a suitable parent which actually supports the given vGPU type. >> >> >> >> > field. The most important thing that libvirt needs to know when >> >> > creating a mdev device for a VM is the mdev type name. The parent >> >> > device should be an optional field to help higher level management >> >> > tools deal with placement of the device for locality or load balancing. >> >> > Also, we can't assume that the parent device is a PCI device, the >> >> > sample mtty driver already breaks this assumption. >> >> >> >> Since we need to assume non-PCI devices and we still need to enable management >> >> to hint libvirt about the parent to utilize load balancing and stuff, I've come >> >> up with the following adjustments/ideas on how to reflect that in the XML: >> >> - still use the address element but use it with the 'type' attribute [1] (still >> >> breaks the sample mtty driver though) while making the element truly optional >> >> if I'm going to be outvoted in favor of scanning the directory for a suitable >> >> parent device on our own, rather than requiring the user to provide that >> >> >> >> - providing either an attribute or a standalone element for the parent device >> >> name, like a string version of the PCI address or whatever form the parent >> >> device comes in (doesn't break the mtty driver but I don't quite like this) >> >> >> >> - providing a path element/attribute to sysfs pointing to the parent device >> >> which I'm afraid is what Daniel is not in favor of libvirt doing >> >> >> >> So, this is what I've so far come up with in terms of hinting libvirt about the >> >> parent device, do you have any input on this, maybe some more ideas on how we >> >> should identify the parent device? >> > >> >IMO, if we cannot account for the mtty sample driver, we're doing it >> >wrong. I suppose we can leave it unspecified how one selects a parent >> >device for the mtty driver, but it should be possible to expand the >> >syntax to include it. So I think that means that when the parent >> >address is provided, the parent address type needs to be specified as >> >PCI. So... >> > >> > <hostdev mode='subsystem' type='mdev'> >> > >> >This needs to encompass the device API or else the optional VM address >> >cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to >> >how we specify the device type for PCI controllers where we have >> >multiple options: >> > >> > <hostdev mode='subsystem' type='mdev' model='vfio-pci'> >> > >> > <source> >> > >> >For managed='no', I don't see that anything other than the mdev UUID is >> >useful. >> > >> > <uuid>MDEV_UUID</uuid> >> > >> >If libvirt gets into the business of creating mdev devices and we call >> >that managed='yes', then the mdev type to create is required. I don't >> >know whether there's anything similar we can steal syntax from: >> > >> > <type>"nvidia-11"</type> >> > >> >That's pretty horrible, needs some xml guru love. >> > >> >We need to provide for specifying a parent, but we can't assume the >> >> From higher level perspective, I believe it would be "good >> enough" for most of the cases to only specify the type. Libvirt will >> anyway have to be able to enumerate the devices for listAllDevices >> afaik. >> >> My wish would be specifying >> <hostdev mode='subsystem' type='mdev'> >> <type>nvidia-11</type> >> </hostdev> >> unless the user has specific requests or some other decision (mmio >> numa placement) takes place. > >Yes, the <type> is the minimum information necessary for libvirt to >create the mdev device itself. A <source> section could add optional >placement information. Note though that without an nvidia-11 type >device on the system to query, the xml doesn't tell us what sort of >device this creates in the VM. We could assume that it's vfio-pci, but >designing in an assumption isn't a great idea. So, as above, some >mechanism to make the xml self contained, such as specifying the model >as vfio-pci, helps avoid that assumption and allows us to know the >format for expressing the VM <address> As long as libvirt provides means to determine the model via device listing (listAllDevices), OK. >> We would additionally need (allocated instances/max instances of that >> type) in listAllDevices to account for the specific assignment >> possibility. > >mdev devices support an available_instances per mdev type that is >dynamically updated as devices are created. The interaction of >available_instances between different types is going to require some >heuristics to understand. Some vendors may not support heterogeneous >types, others may pull from a common pool of resources, where each type >may consume resources from that pool at different rates. Given common pool semantics, will we be able to calculate how many of each type will be available in the pool if we were to instantiate certain type? Example: available types: type_a: 4 devices (each consumes 1 "slot") type_b: 1 device (each consumes 4 "slots") total "slots": 4 we know that creating type_a device prevents any more type_b devices to be created. Does NVIDIA or AMD use the common pool? >> I'm not sure what the decision was wrt type naming, can 2 different >> cards have similarly named type with different meaning? > >We don't deal in similarities, each type ID is unique and it's up to >the mdev vendor driver to make sure that an "nvidia-11" on and M60 card >is software equivalent to an "nvidia-11" on an M10 card. If they're >not equivalent, the type ID will be different. Something we may want >to consider eventually is whether we want/need to deal with >compatibility strings. For instance, NVIDIA seems to be tying the type >ID strongly to specific implementations, an nvidia-11 may only be >available on an M60 card. An M10 card may offer an nvidia-21 type with >similar capabilities. There may be a need to express an mdev device as >compatible with various type IDs for hardware availability, at the risk >of exposing slight variations to the VM. This could also make >placement easier for vendor drivers that only support homogeneous mdev >devices, "I prefer an mdev ID of type 'nvidia-11', but will accept one >of type 'nvidia-12,nvidia-21'". Thanks, I like the idea of libvirt being able to select one of specified types, we have to bear in mind that it'll slightly complicate the XML: <mdev_types> <type>nvidia-11</type> <type>nvidia-21</type> </mdev_types> That luckily shouldn't be problem for libvirt or management software. On the other hand, the type equivalence will require some kind of labeling on the management side -- user defines "mygpu" as "vgpu with type nvidia-11 or nvidia-21" unless libvirt commits to a maintaining a database with capability-equivalent types for devices (which, given the generic-ness of the mdev, doesn't seem like a good idea). >Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Wed, Feb 15, 2017 at 09:50:03AM +0100, Martin Polednik wrote: > On 14/02/17 09:58 -0700, Alex Williamson wrote: > > On Tue, 14 Feb 2017 16:50:14 +0100 > > Martin Polednik <mpolednik@redhat.com> wrote: > > > > > On 07/02/17 12:29 -0700, Alex Williamson wrote: > > > >On Tue, 7 Feb 2017 17:26:51 +0100 > > > >Erik Skultety <eskultet@redhat.com> wrote: > > > > > > > >> On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: > > > >> > On Mon, 6 Feb 2017 13:19:42 +0100 > > > >> > Erik Skultety <eskultet@redhat.com> wrote: > > > >> > > > > >> > > Finally. It's here. This is the initial suggestion on how libvirt might > > > >> > > interract with the mdev framework, currently only focussing on the non-managed > > > >> > > devices, i.e. those pre-created by the user, since that will be revisited once > > > >> > > we all settled on how the XML should look like, given we might not want to use > > > >> > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > > >> > > XML is the following: > > > >> > > > > > >> > > <hostdev mode='subsystem' type='mdev'> > > > >> > > <source> > > > >> > > <!-- this is the host's physical device address --> > > > >> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > > >> > > <uuid>vGPU_UUID<uuid> > > > >> > > <source> > > > >> > > <!-- target PCI address can be omitted to assign it automatically --> > > > >> > > </hostdev> > > > >> > > > > > >> > > So the mediated device is identified by the physical parent device visible on > > > >> > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > > >> > > which we then put on the QEMU's command line. > > > >> > > > > >> > Based on your test code, I think you're creating something like this: > > > >> > > > > >> > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc > > > >> > > > > >> > That would explain the need for the parent device address, but that's > > > >> > an entirely self inflicted requirement. For a managed="no" scenarios, > > > >> > we shouldn't need the parent, we can get to the mdev device > > > >> > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it > > > >> > > > >> True, for managed="no" would this path be a nice optimization. > > > >> > > > >> > seems that the UUID should be the only required source element for > > > >> > managed="no". > > > >> > > > > >> > For managed="yes", it seems like the parent device is still an optional > > > >> > > > >> The reason I went with the parent address element (and purposely neglecting the > > > >> sample mtty driver) was that I assumed any modern mdev capable HW would be > > > >> accessible through the PCI bus on the host. Also I wanted to explicitly hint > > > >> libvirt as much as possible which parent device a vGPU device instance should > > > >> be created on in case there are more than one of them, rather then scanning > > > >> sysfs for a suitable parent which actually supports the given vGPU type. > > > >> > > > >> > field. The most important thing that libvirt needs to know when > > > >> > creating a mdev device for a VM is the mdev type name. The parent > > > >> > device should be an optional field to help higher level management > > > >> > tools deal with placement of the device for locality or load balancing. > > > >> > Also, we can't assume that the parent device is a PCI device, the > > > >> > sample mtty driver already breaks this assumption. > > > >> > > > >> Since we need to assume non-PCI devices and we still need to enable management > > > >> to hint libvirt about the parent to utilize load balancing and stuff, I've come > > > >> up with the following adjustments/ideas on how to reflect that in the XML: > > > >> - still use the address element but use it with the 'type' attribute [1] (still > > > >> breaks the sample mtty driver though) while making the element truly optional > > > >> if I'm going to be outvoted in favor of scanning the directory for a suitable > > > >> parent device on our own, rather than requiring the user to provide that > > > >> > > > >> - providing either an attribute or a standalone element for the parent device > > > >> name, like a string version of the PCI address or whatever form the parent > > > >> device comes in (doesn't break the mtty driver but I don't quite like this) > > > >> > > > >> - providing a path element/attribute to sysfs pointing to the parent device > > > >> which I'm afraid is what Daniel is not in favor of libvirt doing > > > >> > > > >> So, this is what I've so far come up with in terms of hinting libvirt about the > > > >> parent device, do you have any input on this, maybe some more ideas on how we > > > >> should identify the parent device? > > > > > > > >IMO, if we cannot account for the mtty sample driver, we're doing it > > > >wrong. I suppose we can leave it unspecified how one selects a parent > > > >device for the mtty driver, but it should be possible to expand the > > > >syntax to include it. So I think that means that when the parent > > > >address is provided, the parent address type needs to be specified as > > > >PCI. So... > > > > > > > > <hostdev mode='subsystem' type='mdev'> > > > > > > > >This needs to encompass the device API or else the optional VM address > > > >cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to > > > >how we specify the device type for PCI controllers where we have > > > >multiple options: > > > > > > > > <hostdev mode='subsystem' type='mdev' model='vfio-pci'> > > > > > > > > <source> > > > > > > > >For managed='no', I don't see that anything other than the mdev UUID is > > > >useful. > > > > > > > > <uuid>MDEV_UUID</uuid> > > > > > > > >If libvirt gets into the business of creating mdev devices and we call > > > >that managed='yes', then the mdev type to create is required. I don't > > > >know whether there's anything similar we can steal syntax from: > > > > > > > > <type>"nvidia-11"</type> > > > > > > > >That's pretty horrible, needs some xml guru love. > > > > > > > >We need to provide for specifying a parent, but we can't assume the > > > > > > From higher level perspective, I believe it would be "good > > > enough" for most of the cases to only specify the type. Libvirt will > > > anyway have to be able to enumerate the devices for listAllDevices > > > afaik. > > > > > > My wish would be specifying > > > <hostdev mode='subsystem' type='mdev'> > > > <type>nvidia-11</type> > > > </hostdev> > > > unless the user has specific requests or some other decision (mmio > > > numa placement) takes place. > > > > Yes, the <type> is the minimum information necessary for libvirt to > > create the mdev device itself. A <source> section could add optional > > placement information. Note though that without an nvidia-11 type > > device on the system to query, the xml doesn't tell us what sort of > > device this creates in the VM. We could assume that it's vfio-pci, but > > designing in an assumption isn't a great idea. So, as above, some > > mechanism to make the xml self contained, such as specifying the model > > as vfio-pci, helps avoid that assumption and allows us to know the > > format for expressing the VM <address> > > As long as libvirt provides means to determine the model via device > listing (listAllDevices), OK. > Yes, libvirt will provide means expose this information. > > > We would additionally need (allocated instances/max instances of that > > > type) in listAllDevices to account for the specific assignment > > > possibility. > > > > mdev devices support an available_instances per mdev type that is > > dynamically updated as devices are created. The interaction of > > available_instances between different types is going to require some > > heuristics to understand. Some vendors may not support heterogeneous > > types, others may pull from a common pool of resources, where each type > > may consume resources from that pool at different rates. > > Given common pool semantics, will we be able to calculate how many of > each type will be available in the pool if we were to instantiate > certain type? Example: > > available types: > type_a: 4 devices (each consumes 1 "slot") > type_b: 1 device (each consumes 4 "slots") > total "slots": 4 > Well, if we could assume that the number of instances for a specific type would always be a power of 2 and the resources are distributed in that manner, then it's simple, you're allocating a resources that a more resource-demanding type would need to instantiate a single device, so you'll end up with one less device for each more resource-demanding type recursively. However, that is a strong assumption to make, so I'm not sure, it's possible that available instances, which only updates once you instantiated a specific type, is the only thing we should rely on. > we know that creating type_a device prevents any > more type_b devices to be created. > > Does NVIDIA or AMD use the common pool? > > > > I'm not sure what the decision was wrt type naming, can 2 different > > > cards have similarly named type with different meaning? > > > > We don't deal in similarities, each type ID is unique and it's up to > > the mdev vendor driver to make sure that an "nvidia-11" on and M60 card > > is software equivalent to an "nvidia-11" on an M10 card. If they're > > not equivalent, the type ID will be different. Something we may want > > to consider eventually is whether we want/need to deal with > > compatibility strings. For instance, NVIDIA seems to be tying the type > > ID strongly to specific implementations, an nvidia-11 may only be > > available on an M60 card. An M10 card may offer an nvidia-21 type with > > similar capabilities. There may be a need to express an mdev device as > > compatible with various type IDs for hardware availability, at the risk > > of exposing slight variations to the VM. This could also make > > placement easier for vendor drivers that only support homogeneous mdev > > devices, "I prefer an mdev ID of type 'nvidia-11', but will accept one > > of type 'nvidia-12,nvidia-21'". Thanks, > > I like the idea of libvirt being able to select one of specified > types, we have to bear in mind that it'll slightly complicate the XML: > > <mdev_types> > <type>nvidia-11</type> > <type>nvidia-21</type> > </mdev_types> ^^ are you referring to nodedev XML or domain XML, because in case of a domain, there should be only one type per <hostdev type='mdev'>. There is also the ongoing question what's the best way to approach creation of mdev with libvirt and we have to be very careful with that so it won't bite us back in the future. However, for 7.4 the priority is to accept a pre-created device and to provide means in the nodedev driver to list all existing mdev devices and their corresponding parent devices. > > That luckily shouldn't be problem for libvirt or management software. > On the other hand, the type equivalence will require some kind of > labeling on the management side -- user defines "mygpu" as "vgpu with > type nvidia-11 or nvidia-21" unless libvirt commits to a maintaining a > database with capability-equivalent types for devices (which, given > the generic-ness of the mdev, doesn't seem like a good idea). > Libvirt definitely shouldn't be handling type compatibility-related issues. As Alex pointed out, this should be vendor driver's responsibility. There's also Intel's KVMGT which has a different approach to it's type IDs. IIUC they based their type IDs on the fraction of actual resources used, i.e. type _1 consumes the whole HW _2 consumes half, etc. but this is a question for Alex as he's been playing with it for some time. Anyhow, from my understanding Intel's types look more generic, thus more compatible with different HW revisions, if so, then in that case by dealing with the type compatibility, libvirt would be tailoring its logic to a specific vendor's use whereas I think libvirt should only focus on interacting with the mdev framework using the data it's got from the user. IOW new mdev-capable HW will be coming out which would in turn just bring more types to deal with. If the vendor driver won't be willing to accept any other type than just the set it's exporting, then I think the management may want to try to compensate for this with the information it can query from libvirt. Erik > > Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Wed, 15 Feb 2017 14:43:22 +0100 Erik Skultety <eskultet@redhat.com> wrote: > On Wed, Feb 15, 2017 at 09:50:03AM +0100, Martin Polednik wrote: > > On 14/02/17 09:58 -0700, Alex Williamson wrote: > > > On Tue, 14 Feb 2017 16:50:14 +0100 > > > Martin Polednik <mpolednik@redhat.com> wrote: > > > > > > > On 07/02/17 12:29 -0700, Alex Williamson wrote: > > > > >On Tue, 7 Feb 2017 17:26:51 +0100 > > > > >Erik Skultety <eskultet@redhat.com> wrote: > > > > > > > > > >> On Mon, Feb 06, 2017 at 09:33:14AM -0700, Alex Williamson wrote: > > > > >> > On Mon, 6 Feb 2017 13:19:42 +0100 > > > > >> > Erik Skultety <eskultet@redhat.com> wrote: > > > > >> > > > > > >> > > Finally. It's here. This is the initial suggestion on how libvirt might > > > > >> > > interract with the mdev framework, currently only focussing on the non-managed > > > > >> > > devices, i.e. those pre-created by the user, since that will be revisited once > > > > >> > > we all settled on how the XML should look like, given we might not want to use > > > > >> > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > > > >> > > XML is the following: > > > > >> > > > > > > >> > > <hostdev mode='subsystem' type='mdev'> > > > > >> > > <source> > > > > >> > > <!-- this is the host's physical device address --> > > > > >> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > > > >> > > <uuid>vGPU_UUID<uuid> > > > > >> > > <source> > > > > >> > > <!-- target PCI address can be omitted to assign it automatically --> > > > > >> > > </hostdev> > > > > >> > > > > > > >> > > So the mediated device is identified by the physical parent device visible on > > > > >> > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > > > >> > > which we then put on the QEMU's command line. > > > > >> > > > > > >> > Based on your test code, I think you're creating something like this: > > > > >> > > > > > >> > -device vfio-pci,sysfsdev=/sys/class/mdev_bus/0000:00:03.0/53764d0e-85a0-42b4-af5c-2046b460b1dc > > > > >> > > > > > >> > That would explain the need for the parent device address, but that's > > > > >> > an entirely self inflicted requirement. For a managed="no" scenarios, > > > > >> > we shouldn't need the parent, we can get to the mdev device > > > > >> > via /sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc. So it > > > > >> > > > > >> True, for managed="no" would this path be a nice optimization. > > > > >> > > > > >> > seems that the UUID should be the only required source element for > > > > >> > managed="no". > > > > >> > > > > > >> > For managed="yes", it seems like the parent device is still an optional > > > > >> > > > > >> The reason I went with the parent address element (and purposely neglecting the > > > > >> sample mtty driver) was that I assumed any modern mdev capable HW would be > > > > >> accessible through the PCI bus on the host. Also I wanted to explicitly hint > > > > >> libvirt as much as possible which parent device a vGPU device instance should > > > > >> be created on in case there are more than one of them, rather then scanning > > > > >> sysfs for a suitable parent which actually supports the given vGPU type. > > > > >> > > > > >> > field. The most important thing that libvirt needs to know when > > > > >> > creating a mdev device for a VM is the mdev type name. The parent > > > > >> > device should be an optional field to help higher level management > > > > >> > tools deal with placement of the device for locality or load balancing. > > > > >> > Also, we can't assume that the parent device is a PCI device, the > > > > >> > sample mtty driver already breaks this assumption. > > > > >> > > > > >> Since we need to assume non-PCI devices and we still need to enable management > > > > >> to hint libvirt about the parent to utilize load balancing and stuff, I've come > > > > >> up with the following adjustments/ideas on how to reflect that in the XML: > > > > >> - still use the address element but use it with the 'type' attribute [1] (still > > > > >> breaks the sample mtty driver though) while making the element truly optional > > > > >> if I'm going to be outvoted in favor of scanning the directory for a suitable > > > > >> parent device on our own, rather than requiring the user to provide that > > > > >> > > > > >> - providing either an attribute or a standalone element for the parent device > > > > >> name, like a string version of the PCI address or whatever form the parent > > > > >> device comes in (doesn't break the mtty driver but I don't quite like this) > > > > >> > > > > >> - providing a path element/attribute to sysfs pointing to the parent device > > > > >> which I'm afraid is what Daniel is not in favor of libvirt doing > > > > >> > > > > >> So, this is what I've so far come up with in terms of hinting libvirt about the > > > > >> parent device, do you have any input on this, maybe some more ideas on how we > > > > >> should identify the parent device? > > > > > > > > > >IMO, if we cannot account for the mtty sample driver, we're doing it > > > > >wrong. I suppose we can leave it unspecified how one selects a parent > > > > >device for the mtty driver, but it should be possible to expand the > > > > >syntax to include it. So I think that means that when the parent > > > > >address is provided, the parent address type needs to be specified as > > > > >PCI. So... > > > > > > > > > > <hostdev mode='subsystem' type='mdev'> > > > > > > > > > >This needs to encompass the device API or else the optional VM address > > > > >cannot be resolved. Perhaps model='vfio-pci' here? Seems similar to > > > > >how we specify the device type for PCI controllers where we have > > > > >multiple options: > > > > > > > > > > <hostdev mode='subsystem' type='mdev' model='vfio-pci'> > > > > > > > > > > <source> > > > > > > > > > >For managed='no', I don't see that anything other than the mdev UUID is > > > > >useful. > > > > > > > > > > <uuid>MDEV_UUID</uuid> > > > > > > > > > >If libvirt gets into the business of creating mdev devices and we call > > > > >that managed='yes', then the mdev type to create is required. I don't > > > > >know whether there's anything similar we can steal syntax from: > > > > > > > > > > <type>"nvidia-11"</type> > > > > > > > > > >That's pretty horrible, needs some xml guru love. > > > > > > > > > >We need to provide for specifying a parent, but we can't assume the > > > > > > > > From higher level perspective, I believe it would be "good > > > > enough" for most of the cases to only specify the type. Libvirt will > > > > anyway have to be able to enumerate the devices for listAllDevices > > > > afaik. > > > > > > > > My wish would be specifying > > > > <hostdev mode='subsystem' type='mdev'> > > > > <type>nvidia-11</type> > > > > </hostdev> > > > > unless the user has specific requests or some other decision (mmio > > > > numa placement) takes place. > > > > > > Yes, the <type> is the minimum information necessary for libvirt to > > > create the mdev device itself. A <source> section could add optional > > > placement information. Note though that without an nvidia-11 type > > > device on the system to query, the xml doesn't tell us what sort of > > > device this creates in the VM. We could assume that it's vfio-pci, but > > > designing in an assumption isn't a great idea. So, as above, some > > > mechanism to make the xml self contained, such as specifying the model > > > as vfio-pci, helps avoid that assumption and allows us to know the > > > format for expressing the VM <address> > > > > As long as libvirt provides means to determine the model via device > > listing (listAllDevices), OK. > > > > Yes, libvirt will provide means expose this information. > > > > > We would additionally need (allocated instances/max instances of that > > > > type) in listAllDevices to account for the specific assignment > > > > possibility. > > > > > > mdev devices support an available_instances per mdev type that is > > > dynamically updated as devices are created. The interaction of > > > available_instances between different types is going to require some > > > heuristics to understand. Some vendors may not support heterogeneous > > > types, others may pull from a common pool of resources, where each type > > > may consume resources from that pool at different rates. > > > > Given common pool semantics, will we be able to calculate how many of > > each type will be available in the pool if we were to instantiate > > certain type? Example: > > > > available types: > > type_a: 4 devices (each consumes 1 "slot") > > type_b: 1 device (each consumes 4 "slots") > > total "slots": 4 > > > > Well, if we could assume that the number of instances for a specific type would > always be a power of 2 and the resources are distributed in that manner, then > it's simple, you're allocating a resources that a more resource-demanding type > would need to instantiate a single device, so you'll end up with one less > device for each more resource-demanding type recursively. However, that is a > strong assumption to make, so I'm not sure, it's possible that available > instances, which only updates once you instantiated a specific type, is the > only thing we should rely on. Agree, and vendors can change how they manage this at any time. For instance if I boot one version of the kernel, i915 gives me: i915-GVTg_V4_1 i915-GVTg_V4_2 i915-GVTg_V4_4 If I boot another, I get: i915-GVTg_V4_1 i915-GVTg_V4_2 i915-GVTg_V4_5 i915-GVTg_V4_7 Now we don't have evenly divisible numbers. If I create a type _1 device, available_instances still says I can create one type _5 or _7. It's perhaps best for libvirt to just look at the current state and not try to predict the future. > > we know that creating type_a device prevents any > > more type_b devices to be created. > > > > Does NVIDIA or AMD use the common pool? AMD isn't a player here yet, Intel and NVIDIA have vGPUs, IBM has a model under development for S390 channel I/O. The only thing you can rely on is available_instances per mdev type at a given point of time. How available_instances chances when we start creating devices is vendor specific and may change at any time. > > > > I'm not sure what the decision was wrt type naming, can 2 different > > > > cards have similarly named type with different meaning? > > > > > > We don't deal in similarities, each type ID is unique and it's up to > > > the mdev vendor driver to make sure that an "nvidia-11" on and M60 card > > > is software equivalent to an "nvidia-11" on an M10 card. If they're > > > not equivalent, the type ID will be different. Something we may want > > > to consider eventually is whether we want/need to deal with > > > compatibility strings. For instance, NVIDIA seems to be tying the type > > > ID strongly to specific implementations, an nvidia-11 may only be > > > available on an M60 card. An M10 card may offer an nvidia-21 type with > > > similar capabilities. There may be a need to express an mdev device as > > > compatible with various type IDs for hardware availability, at the risk > > > of exposing slight variations to the VM. This could also make > > > placement easier for vendor drivers that only support homogeneous mdev > > > devices, "I prefer an mdev ID of type 'nvidia-11', but will accept one > > > of type 'nvidia-12,nvidia-21'". Thanks, > > > > I like the idea of libvirt being able to select one of specified > > types, we have to bear in mind that it'll slightly complicate the XML: > > > > <mdev_types> > > <type>nvidia-11</type> > > <type>nvidia-21</type> > > </mdev_types> > > ^^ are you referring to nodedev XML or domain XML, because in case of a domain, > there should be only one type per <hostdev type='mdev'>. There is also the > ongoing question what's the best way to approach creation of mdev with libvirt > and we have to be very careful with that so it won't bite us back in the > future. > However, for 7.4 the priority is to accept a pre-created device and to provide > means in the nodedev driver to list all existing mdev devices and their > corresponding parent devices. Sorry if I confused the topic with some sort of compatibility listing. I agree that for a <hostdev> there needs to be a single type if libvirt is to create an instance of that type. Any notion of compatible or secondary acceptable types is lower priority than the necessary basic behaviors, I'm just trying to plan ahead for later extensions that might be useful. Perhaps any notion of compatibility lives in user define lists above libvirt. > > That luckily shouldn't be problem for libvirt or management software. > > On the other hand, the type equivalence will require some kind of > > labeling on the management side -- user defines "mygpu" as "vgpu with > > type nvidia-11 or nvidia-21" unless libvirt commits to a maintaining a > > database with capability-equivalent types for devices (which, given > > the generic-ness of the mdev, doesn't seem like a good idea). > > > > Libvirt definitely shouldn't be handling type compatibility-related issues. > As Alex pointed out, this should be vendor driver's responsibility. There's > also Intel's KVMGT which has a different approach to it's type IDs. IIUC they > based their type IDs on the fraction of actual resources used, i.e. type _1 > consumes the whole HW _2 consumes half, etc. but this is a question for Alex as > he's been playing with it for some time. Anyhow, from my understanding Intel's > types look more generic, thus more compatible with different HW revisions, if > so, then in that case by dealing with the type compatibility, libvirt would be > tailoring its logic to a specific vendor's use whereas I think libvirt > should only focus on interacting with the mdev framework using the data it's > got from the user. IOW new mdev-capable HW will be coming out which would in > turn just bring more types to deal with. If the vendor driver won't be willing > to accept any other type than just the set it's exporting, then I think the > management may want to try to compensate for this with the information it can > query from libvirt. AIUI, looking at the example Intel mdev types I list above, that "V4" indicates a Broadwell class GPU. So don't be fooled into thinking Intel is making some sort of generic device that it can represent on any platform. I'd expect a Skylake system to export similar types, but with a "V5" component to the name. NVIDIA naming is just more opaque, possibly changing not only across generations but across implementations. I fully agree that it's the vendor's responsibility to maintain that a given type is compatible wherever it is exposed and libvirt's first priority is to focus on specifying a single type in the xml and working towards instantiating an mdev of that type. Libvirt should never assume that anything other than that single, exact type is compatible or sufficient for the VM. I did plant the seed above about whether user defined compatibility lists might be useful, it seems like something we should keep in mind, but at a lower priority than any sort of initial support. As Erik suggested in a separate discussion, perhaps any notion of user defined compatibility happens at a management layer above libvirt. Migration also needs to be considered when we think about compatible devices. Compatibility likely only refers to the point at which we instantiate the VM, if we were ever to support migration of an mdev device, the target and source would need to be identical. Yet more reasons for libvirt to leave compatibility to higher layers of management tools. Thanks, Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Mon, Feb 06, 2017 at 01:19:42PM +0100, Erik Skultety wrote: > Finally. It's here. This is the initial suggestion on how libvirt might > interract with the mdev framework, currently only focussing on the non-managed > devices, i.e. those pre-created by the user, since that will be revisited once > we all settled on how the XML should look like, given we might not want to use > the sysfs path directly as an attribute in the domain XML. My proposal on the > XML is the following: > > <hostdev mode='subsystem' type='mdev'> > <source> > <!-- this is the host's physical device address --> > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > <uuid>vGPU_UUID<uuid> > <source> > <!-- target PCI address can be omitted to assign it automatically --> > </hostdev> > > So the mediated device is identified by the physical parent device visible on > the host and a UUID which allows us to construct the sysfs path by ourselves, > which we then put on the QEMU's command line. > > A few remarks if you actually happen to have a machine to test this on: > - right now the mediated devices are one-time use only, i.e. they have to be > recreated before every machine boot > - I wouldn't recommend assigning multiple vGPUs to a single domain > > Once this series is sorted out, we can then continue with 'managed=yes' where > as Laine pointed out [1], we need to figure out how exactly should the > management layer hint libvirt which vGPU type should be used for device > instantiation. You seem to be suggesting that managed=yes with mdev devices would cause create / delete of a mdev device from a specified parent. This is rather different semantics from what managed=yes does with PCI device assignment today. There the managed=yes flag is just about controlling host device driver attachment. ie whether libvirt will manually bind to vfio.ko, or expect the admin to have bound it to vfio.ko before hand. I think it is important to keep that concept as is for mdev too. While we're thinking of mdev purely in terms of KVM + vfio usage, it wouldn't suprise me if there ended up being non-KVM based use cases for mdev. It isn't clear to me that auto-creation of mdev devices as a concept even belongs in the domain XML neccessarily. Looking at two similar areas. For SRIOV NICs, in the domain XML you either specify an explicit VF to use, or you reference a libvirt virtual network. The latter takes care of dynamically providing VFs to VMs. For NPIV, IIRC, the domain XML works similarly either taking an explicit vHBA, or referencing a storage pool to get one more dynamically. Before we even consider auto-creation though, I think we need to have manual creation designed & integrated in the node device APIs. So in terms of the domain XML, I think the only think we need to provide is the address of the pre-existing mdev device to be used. In this case "address" means the UUID. We should not need anything about the parent device AFAICT. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Mon, 6 Feb 2017 16:44:37 +0000 "Daniel P. Berrange" <berrange@redhat.com> wrote: > On Mon, Feb 06, 2017 at 01:19:42PM +0100, Erik Skultety wrote: > > Finally. It's here. This is the initial suggestion on how libvirt might > > interract with the mdev framework, currently only focussing on the non-managed > > devices, i.e. those pre-created by the user, since that will be revisited once > > we all settled on how the XML should look like, given we might not want to use > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > XML is the following: > > > > <hostdev mode='subsystem' type='mdev'> > > <source> > > <!-- this is the host's physical device address --> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > <uuid>vGPU_UUID<uuid> > > <source> > > <!-- target PCI address can be omitted to assign it automatically --> > > </hostdev> > > > > So the mediated device is identified by the physical parent device visible on > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > which we then put on the QEMU's command line. > > > > A few remarks if you actually happen to have a machine to test this on: > > - right now the mediated devices are one-time use only, i.e. they have to be > > recreated before every machine boot > > - I wouldn't recommend assigning multiple vGPUs to a single domain > > > > Once this series is sorted out, we can then continue with 'managed=yes' where > > as Laine pointed out [1], we need to figure out how exactly should the > > management layer hint libvirt which vGPU type should be used for device > > instantiation. > > You seem to be suggesting that managed=yes with mdev devices would > cause create / delete of a mdev device from a specified parent. > > This is rather different semantics from what managed=yes does with > PCI device assignment today. There the managed=yes flag is just > about controlling host device driver attachment. ie whether libvirt > will manually bind to vfio.ko, or expect the admin to have bound > it to vfio.ko before hand. I think it is important to keep that > concept as is for mdev too. > > While we're thinking of mdev purely in terms of KVM + vfio usage, > it wouldn't suprise me if there ended up being non-KVM based > use cases for mdev. > > It isn't clear to me that auto-creation of mdev devices as a concept > even belongs in the domain XML neccessarily. > > Looking at two similar areas. For SRIOV NICs, in the domain XML > you either specify an explicit VF to use, or you reference a > libvirt virtual network. The latter takes care of dynamically > providing VFs to VMs. For NPIV, IIRC, the domain XML works > similarly either taking an explicit vHBA, or referencing a > storage pool to get one more dynamically. Nit, there are other constraints of SR-IOV which I think are over simplifying this analogy. With SR-IOV, we can't dynamically instantiate new VFs individually. The process there requires that we set the number of VFs we need and enable them. Changing that number of VFs requires that all existing VFs on that PF are removed and recreated. So, does libvirt work the way it does with SR-IOV devices because that's the optimal way for users to make use of those VFs, or does it behave that way because it must to follow the constraints of the device? I think libvirt handles VFs much like it does PFs because it has no other choice. Here we do have a choice. Individual mdev devices can be created and destroyed. The only dependency between mdev devices is how creating one affects the availability of mdev types remaining on the parent device. It would really be a shame to not take advantage of the fact that the underlying device creation has advanced so far from SR-IOV and lump it into the same sort of management. My impression is that user management of creating SR-IOV VFs via module options or self defined scripts is a stumbling point that libvirt could help to address here. > Before we even consider auto-creation though, I think we need > to have manual creation designed & integrated in the node device > APIs. > > So in terms of the domain XML, I think the only think we need > to provide is the address of the pre-existing mdev device > to be used. In this case "address" means the UUID. We should > not need anything about the parent device AFAICT. Yep, agree. Thanks, Alex -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Mon, Feb 06, 2017 at 04:44:37PM +0000, Daniel P. Berrange wrote: > On Mon, Feb 06, 2017 at 01:19:42PM +0100, Erik Skultety wrote: > > Finally. It's here. This is the initial suggestion on how libvirt might > > interract with the mdev framework, currently only focussing on the non-managed > > devices, i.e. those pre-created by the user, since that will be revisited once > > we all settled on how the XML should look like, given we might not want to use > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > XML is the following: > > > > <hostdev mode='subsystem' type='mdev'> > > <source> > > <!-- this is the host's physical device address --> > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > <uuid>vGPU_UUID<uuid> > > <source> > > <!-- target PCI address can be omitted to assign it automatically --> > > </hostdev> > > > > So the mediated device is identified by the physical parent device visible on > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > which we then put on the QEMU's command line. > > > > A few remarks if you actually happen to have a machine to test this on: > > - right now the mediated devices are one-time use only, i.e. they have to be > > recreated before every machine boot > > - I wouldn't recommend assigning multiple vGPUs to a single domain > > > > Once this series is sorted out, we can then continue with 'managed=yes' where > > as Laine pointed out [1], we need to figure out how exactly should the > > management layer hint libvirt which vGPU type should be used for device > > instantiation. > > You seem to be suggesting that managed=yes with mdev devices would > cause create / delete of a mdev device from a specified parent. > > This is rather different semantics from what managed=yes does with > PCI device assignment today. There the managed=yes flag is just > about controlling host device driver attachment. ie whether libvirt > will manually bind to vfio.ko, or expect the admin to have bound > it to vfio.ko before hand. I think it is important to keep that > concept as is for mdev too. If the managed attribute was used with other devices beside PCI, then sure, we should keep the concept, however, since only PCI devices support it and now we have another device type that potentially might have a use for such an attribute I think it's perfectly reasonable to alter the logic behind that attribute in favor of the new possibilities to device management which mdev framework is providing us with which in this case is dynamic creation and removal of a mediated device. > > While we're thinking of mdev purely in terms of KVM + vfio usage, > it wouldn't suprise me if there ended up being non-KVM based > use cases for mdev. > > It isn't clear to me that auto-creation of mdev devices as a concept > even belongs in the domain XML neccessarily. > > Looking at two similar areas. For SRIOV NICs, in the domain XML > you either specify an explicit VF to use, or you reference a > libvirt virtual network. The latter takes care of dynamically > providing VFs to VMs. For NPIV, IIRC, the domain XML works > similarly either taking an explicit vHBA, or referencing a > storage pool to get one more dynamically. > > Before we even consider auto-creation though, I think we need > to have manual creation designed & integrated in the node device > APIs. > Yes, integrating mdev into the nodedev driver this way ^^ is definitely planned. > So in terms of the domain XML, I think the only think we need > to provide is the address of the pre-existing mdev device > to be used. In this case "address" means the UUID. We should > not need anything about the parent device AFAICT. > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
On Tue, Feb 07, 2017 at 05:48:23PM +0100, Erik Skultety wrote: > On Mon, Feb 06, 2017 at 04:44:37PM +0000, Daniel P. Berrange wrote: > > On Mon, Feb 06, 2017 at 01:19:42PM +0100, Erik Skultety wrote: > > > Finally. It's here. This is the initial suggestion on how libvirt might > > > interract with the mdev framework, currently only focussing on the non-managed > > > devices, i.e. those pre-created by the user, since that will be revisited once > > > we all settled on how the XML should look like, given we might not want to use > > > the sysfs path directly as an attribute in the domain XML. My proposal on the > > > XML is the following: > > > > > > <hostdev mode='subsystem' type='mdev'> > > > <source> > > > <!-- this is the host's physical device address --> > > > <address domain='0x0000' bus='0x00' slot='0x00' function='0x00'> > > > <uuid>vGPU_UUID<uuid> > > > <source> > > > <!-- target PCI address can be omitted to assign it automatically --> > > > </hostdev> > > > > > > So the mediated device is identified by the physical parent device visible on > > > the host and a UUID which allows us to construct the sysfs path by ourselves, > > > which we then put on the QEMU's command line. > > > > > > A few remarks if you actually happen to have a machine to test this on: > > > - right now the mediated devices are one-time use only, i.e. they have to be > > > recreated before every machine boot > > > - I wouldn't recommend assigning multiple vGPUs to a single domain > > > > > > Once this series is sorted out, we can then continue with 'managed=yes' where > > > as Laine pointed out [1], we need to figure out how exactly should the > > > management layer hint libvirt which vGPU type should be used for device > > > instantiation. > > > > You seem to be suggesting that managed=yes with mdev devices would > > cause create / delete of a mdev device from a specified parent. > > > > This is rather different semantics from what managed=yes does with > > PCI device assignment today. There the managed=yes flag is just > > about controlling host device driver attachment. ie whether libvirt > > will manually bind to vfio.ko, or expect the admin to have bound > > it to vfio.ko before hand. I think it is important to keep that > > concept as is for mdev too. > > If the managed attribute was used with other devices beside PCI, then sure, we > should keep the concept, however, since only PCI devices support it and now we > have another device type that potentially might have a use for such an > attribute I think it's perfectly reasonable to alter the logic behind that > attribute in favor of the new possibilities to device management which mdev > framework is providing us with which in this case is dynamic creation and > removal of a mediated device. No we really shouldn't use one attribute to overload completely different semantics. As I say, we may well find we want to implement the existing PCI semantics for mdev devices too. If we want to auto-create, that should be a different attribute eg 'autocreate=yes|no' Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
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