usb-storage is a compound device that automatically creates a USB mass
storage device and a SCSI device as its backend. Unfortunately it lacks
some configuration options that are usually present with a SCSI device,
and cannot represent CD-ROM in particular.
Replace usb-storage with usb-bot, which can be combined with a manually
created SCSI device. libvirt will configure the SCSI device in a way
identical with how QEMU does for usb-storage except that now it respects
a configuration option to represent CD-ROM.
Resolves: https://gitlab.com/libvirt/libvirt/-/issues/368
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
src/qemu/qemu_alias.c | 3 +-
src/qemu/qemu_capabilities.c | 2 +-
src/qemu/qemu_command.c | 55 ++++++++++++++++++++--
src/qemu/qemu_command.h | 5 ++
src/qemu/qemu_hotplug.c | 34 ++++++++++---
src/qemu/qemu_validate.c | 4 +-
tests/qemuhotplugtest.c | 8 +++-
.../qemuxmlconfdata/disk-cache.x86_64-latest.args | 3 +-
.../disk-cdrom-bus-other.x86_64-latest.args | 3 +-
.../disk-device-removable.x86_64-latest.args | 3 +-
.../disk-usb-device.x86_64-latest.args | 3 +-
11 files changed, 102 insertions(+), 21 deletions(-)
diff --git a/src/qemu/qemu_alias.c b/src/qemu/qemu_alias.c
index 3e6bced4a88538a040dd8a65f40dc9f7f56b8ec9..64986368d0588f7778c8e3a09ae3169c1961b456 100644
--- a/src/qemu/qemu_alias.c
+++ b/src/qemu/qemu_alias.c
@@ -267,8 +267,7 @@ qemuAssignDeviceDiskAlias(virDomainDef *def,
break;
case VIR_DOMAIN_DISK_BUS_USB:
- diskPriv->qomName = g_strdup_printf("/machine/peripheral/%s/%s.0/legacy[0]",
- disk->info.alias, disk->info.alias);
+ diskPriv->qomName = g_strconcat("scsi", disk->info.alias, NULL);
break;
case VIR_DOMAIN_DISK_BUS_XEN:
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 2c7f9cfe994c45dd3bbecc9cd9fff51889adfb0f..b253cb407e8334320cc8ecd49d28d2481d82e9b4 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -6477,7 +6477,7 @@ virQEMUCapsFillDomainDeviceDiskCaps(virQEMUCaps *qemuCaps,
VIR_DOMAIN_DISK_BUS_VIRTIO,
/* VIR_DOMAIN_DISK_BUS_SD */);
- if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_USB_STORAGE))
+ if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_USB_BOT))
VIR_DOMAIN_CAPS_ENUM_SET(disk->bus, VIR_DOMAIN_DISK_BUS_USB);
if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ICH9_AHCI))
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 0ad73af335974a236341fa85d02c83f14af08934..29db916e70804ec482392c078a280904a992eaf3 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1611,6 +1611,31 @@ qemuBuildIothreadMappingProps(GSList *iothreads)
return g_steal_pointer(&ret);
}
+int
+qemuBuildDiskBusProps(const virDomainDef *def,
+ const virDomainDiskDef *disk,
+ virJSONValue **propsRet)
+{
+ g_autoptr(virJSONValue) props = NULL;
+
+ *propsRet = NULL;
+
+ if (disk->bus != VIR_DOMAIN_DISK_BUS_USB)
+ return 0;
+
+ if (virJSONValueObjectAdd(&props,
+ "s:driver", "usb-bot",
+ "s:id", disk->info.alias,
+ NULL) < 0)
+ return -1;
+
+ if (qemuBuildDeviceAddressProps(props, def, &disk->info) < 0)
+ return -1;
+
+ *propsRet = g_steal_pointer(&props);
+
+ return 0;
+}
virJSONValue *
qemuBuildDiskDeviceProps(const virDomainDef *def,
@@ -1619,6 +1644,7 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
{
g_autoptr(virJSONValue) props = NULL;
const char *driver = NULL;
+ g_autofree char *usbBusId = NULL;
g_autofree char *scsiVPDDeviceId = NULL;
virTristateSwitch shareRW = VIR_TRISTATE_SWITCH_ABSENT;
g_autofree char *chardev = NULL;
@@ -1637,6 +1663,7 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
const char *rpolicy = NULL;
const char *model = NULL;
const char *product = NULL;
+ const char *id = disk->info.alias;
switch (disk->bus) {
case VIR_DOMAIN_DISK_BUS_IDE:
@@ -1650,6 +1677,17 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
break;
+ case VIR_DOMAIN_DISK_BUS_USB:
+ usbBusId = g_strconcat(disk->info.alias, ".0", NULL);
+ if (virJSONValueObjectAdd(&props,
+ "s:bus", usbBusId,
+ "u:scsi-id", 0,
+ "u:lun", 0,
+ NULL) < 0)
+ return NULL;
+
+ id = QEMU_DOMAIN_DISK_PRIVATE(disk)->qomName;
+ G_GNUC_FALLTHROUGH;
case VIR_DOMAIN_DISK_BUS_SCSI:
if (disk->device == VIR_DOMAIN_DISK_DEVICE_LUN) {
driver = "scsi-block";
@@ -1719,8 +1757,6 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
}
break;
- case VIR_DOMAIN_DISK_BUS_USB:
- driver = "usb-storage";
if (disk->removable == VIR_TRISTATE_SWITCH_ABSENT)
removable = VIR_TRISTATE_SWITCH_OFF;
@@ -1755,7 +1791,8 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
if (disk->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_DRIVE)
disk->info.addr.drive.diskbus = disk->bus;
- if (qemuBuildDeviceAddressProps(props, def, &disk->info) < 0)
+ if (disk->bus != VIR_DOMAIN_DISK_BUS_USB &&
+ qemuBuildDeviceAddressProps(props, def, &disk->info) < 0)
return NULL;
if (disk->src->shared)
@@ -1816,7 +1853,7 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
"T:share-rw", shareRW,
"S:drive", drive,
"S:chardev", chardev,
- "s:id", disk->info.alias,
+ "s:id", id,
"p:bootindex", bootindex,
"S:loadparm", bootLoadparm,
"p:logical_block_size", logical_block_size,
@@ -2110,6 +2147,16 @@ qemuBuildDiskCommandLine(virCommand *cmd,
if (qemuCommandAddExtDevice(cmd, &disk->info, def, qemuCaps) < 0)
return -1;
+ if (qemuBuildDiskBusProps(def, disk, &devprops) < 0)
+ return -1;
+
+ if (devprops) {
+ if (qemuBuildDeviceCommandlineFromJSON(cmd, devprops, def, qemuCaps) < 0)
+ return -1;
+
+ g_clear_pointer(&devprops, virJSONValueFree);
+ }
+
if (!(devprops = qemuBuildDiskDeviceProps(def, disk, qemuCaps)))
return -1;
diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
index 76c514b5f744c60e433f0d8d8760a8730c886eed..48b8ed8ac58d005503c8bdb7e255af097a548fd9 100644
--- a/src/qemu/qemu_command.h
+++ b/src/qemu/qemu_command.h
@@ -116,6 +116,11 @@ qemuBlockStorageSourceChainData *
qemuBuildStorageSourceChainAttachPrepareBlockdevTop(virStorageSource *top,
virStorageSource *backingStore);
+int
+qemuBuildDiskBusProps(const virDomainDef *def,
+ const virDomainDiskDef *disk,
+ virJSONValue **propsRet);
+
virJSONValue *
qemuBuildDiskDeviceProps(const virDomainDef *def,
virDomainDiskDef *disk,
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index 28ca321c5c194678d25d67aa02ec82c13175f4f5..cfbaf195bd0a8991c8902795560bda3ee85e42bc 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -31,6 +31,7 @@
#include "qemu_command.h"
#include "qemu_hostdev.h"
#include "qemu_interface.h"
+#include "qemu_monitor_json.h"
#include "qemu_passt.h"
#include "qemu_process.h"
#include "qemu_security.h"
@@ -709,8 +710,10 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
{
g_autoptr(qemuBlockStorageSourceChainData) data = NULL;
qemuDomainObjPrivate *priv = vm->privateData;
+ g_autoptr(virJSONValue) busprops = NULL;
g_autoptr(virJSONValue) devprops = NULL;
bool extensionDeviceAttached = false;
+ bool busAdded = false;
int rc;
g_autoptr(qemuSnapshotDiskContext) transientDiskSnapshotCtxt = NULL;
bool origReadonly = disk->src->readonly;
@@ -766,6 +769,9 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
}
}
+ if (qemuBuildDiskBusProps(vm->def, disk, &busprops) < 0)
+ goto rollback;
+
if (!(devprops = qemuBuildDiskDeviceProps(vm->def, disk, priv->qemuCaps)))
goto rollback;
@@ -775,16 +781,20 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
if ((rc = qemuDomainAttachExtensionDevice(priv->mon, &disk->info)) == 0)
extensionDeviceAttached = true;
+ if (rc == 0 && busprops &&
+ (rc = qemuMonitorAddDeviceProps(priv->mon, &busprops)) == 0)
+ busAdded = true;
+
if (rc == 0)
rc = qemuMonitorAddDeviceProps(priv->mon, &devprops);
- /* Setup throttling of disk via block_set_io_throttle QMP command. This
- * is a hack until the 'throttle' blockdev driver will support modification
- * of the trhottle group. See also qemuProcessSetupDiskThrottlingBlockdev.
- * As there isn't anything sane to do if this fails, let's just return
- * success.
- */
if (rc == 0) {
+ /* Setup throttling of disk via block_set_io_throttle QMP command. This
+ * is a hack until the 'throttle' blockdev driver will support modification
+ * of the trhottle group. See also qemuProcessSetupDiskThrottlingBlockdev.
+ * As there isn't anything sane to do if this fails, let's just return
+ * success.
+ */
qemuDomainDiskPrivate *diskPriv = QEMU_DOMAIN_DISK_PRIVATE(disk);
g_autoptr(GHashTable) blockinfo = NULL;
@@ -801,6 +811,15 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
qemuProcessRefreshDiskProps(disk, diskinfo);
}
}
+
+ if (disk->bus == VIR_DOMAIN_DISK_BUS_USB) {
+ qemuMonitorJSONObjectProperty prop = {
+ .type = QEMU_MONITOR_OBJECT_PROPERTY_BOOLEAN,
+ .val.b = true,
+ };
+
+ rc = qemuMonitorJSONSetObjectProperty(priv->mon, disk->info.alias, "attached", &prop);
+ }
}
qemuDomainObjExitMonitor(vm);
@@ -814,6 +833,9 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
if (qemuDomainObjEnterMonitorAsync(vm, asyncJob) < 0)
return -1;
+ if (busAdded)
+ ignore_value(qemuMonitorDelDevice(priv->mon, disk->info.alias));
+
if (extensionDeviceAttached)
ignore_value(qemuDomainDetachExtensionDevice(priv->mon, &disk->info));
diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index f3ef1be660b1cbbfe8ed5643baf2e9f4a63cf60d..f9ec3a7c076c3755e1c3ddf3c63aeeb7ed576f2b 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -3146,9 +3146,9 @@ qemuValidateDomainDeviceDefDiskFrontend(const virDomainDiskDef *disk,
break;
case VIR_DOMAIN_DISK_BUS_USB:
- if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_USB_STORAGE)) {
+ if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_USB_BOT)) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
- _("This QEMU doesn't support '-device usb-storage'"));
+ _("This QEMU doesn't support '-device usb-bot'"));
return -1;
}
diff --git a/tests/qemuhotplugtest.c b/tests/qemuhotplugtest.c
index d2a1f5acf1c17236f0cc038fda43e4f3052cc28b..96ab222836f2594ce7dbd88236ebfe704c18838b 100644
--- a/tests/qemuhotplugtest.c
+++ b/tests/qemuhotplugtest.c
@@ -590,7 +590,9 @@ mymain(void)
DO_TEST_ATTACH("x86_64", "base-live", "disk-usb", false, true,
"blockdev-add", QMP_OK,
"device_add", QMP_OK,
- "query-block", QMP_EMPTY_ARRAY);
+ "device_add", QMP_OK,
+ "query-block", QMP_EMPTY_ARRAY,
+ "qom-set", QMP_OK);
DO_TEST_DETACH("x86_64", "base-live", "disk-usb", true, true,
"device_del", QMP_OK);
DO_TEST_DETACH("x86_64", "base-live", "disk-usb", false, false,
@@ -746,7 +748,9 @@ mymain(void)
DO_TEST_ATTACH("x86_64", "base-live", "cdrom-usb", false, true,
"blockdev-add", QMP_OK,
"device_add", QMP_OK,
- "query-block", QMP_EMPTY_ARRAY);
+ "device_add", QMP_OK,
+ "query-block", QMP_EMPTY_ARRAY,
+ "qom-set", QMP_OK);
DO_TEST_DETACH("x86_64", "base-live", "cdrom-usb", true, true,
"device_del", QMP_OK);
DO_TEST_DETACH("x86_64", "base-live", "cdrom-usb", false, false,
diff --git a/tests/qemuxmlconfdata/disk-cache.x86_64-latest.args b/tests/qemuxmlconfdata/disk-cache.x86_64-latest.args
index 27be6441774b13dc0c491328431aed6ccd3eddaa..206f8ab9ca46008ff1895730159838aa7dd1e018 100644
--- a/tests/qemuxmlconfdata/disk-cache.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/disk-cache.x86_64-latest.args
@@ -42,7 +42,8 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
-device '{"driver":"virtio-blk-pci","bus":"pci.0","addr":"0x3","drive":"libvirt-2-format","id":"virtio-disk0","write-cache":"off"}' \
-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap","cache":{"direct":true,"no-flush":false}}' \
-blockdev '{"node-name":"libvirt-1-format","read-only":false,"cache":{"direct":true,"no-flush":false},"driver":"qcow2","file":"libvirt-1-storage"}' \
--device '{"driver":"usb-storage","bus":"usb.0","port":"1","drive":"libvirt-1-format","id":"usb-disk1","removable":false,"write-cache":"off"}' \
+-device '{"driver":"usb-bot","id":"usb-disk1","bus":"usb.0","port":"1"}' \
+-device '{"bus":"usb-disk1.0","scsi-id":0,"lun":0,"driver":"scsi-hd","device_id":"drive-usb-disk1","drive":"libvirt-1-format","id":"scsiusb-disk1","write-cache":"off"}' \
-audiodev '{"id":"audio1","driver":"none"}' \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
diff --git a/tests/qemuxmlconfdata/disk-cdrom-bus-other.x86_64-latest.args b/tests/qemuxmlconfdata/disk-cdrom-bus-other.x86_64-latest.args
index e1406af663625bbb1c27203450bc0135af3861e7..8e5c60ac1ec185d1b717b3b22ceb07b721b54846 100644
--- a/tests/qemuxmlconfdata/disk-cdrom-bus-other.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/disk-cdrom-bus-other.x86_64-latest.args
@@ -28,7 +28,8 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
-boot strict=on \
-device '{"driver":"piix3-usb-uhci","id":"usb","bus":"pci.0","addr":"0x1.0x2"}' \
-blockdev '{"driver":"file","filename":"/root/boot.iso","node-name":"libvirt-1-storage","read-only":true}' \
--device '{"driver":"usb-storage","bus":"usb.0","port":"1","drive":"libvirt-1-storage","id":"usb-disk0","removable":false}' \
+-device '{"driver":"usb-bot","id":"usb-disk0","bus":"usb.0","port":"1"}' \
+-device '{"bus":"usb-disk0.0","scsi-id":0,"lun":0,"driver":"scsi-cd","device_id":"drive-usb-disk0","drive":"libvirt-1-storage","id":"scsiusb-disk0"}' \
-audiodev '{"id":"audio1","driver":"none"}' \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
-msg timestamp=on
diff --git a/tests/qemuxmlconfdata/disk-device-removable.x86_64-latest.args b/tests/qemuxmlconfdata/disk-device-removable.x86_64-latest.args
index e0701f4bd25d79b60dc4f9294a603d0a7cd9f0b1..d9b259bc59cc54b10ede57e696e553b3d5f2ef06 100644
--- a/tests/qemuxmlconfdata/disk-device-removable.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/disk-device-removable.x86_64-latest.args
@@ -31,7 +31,8 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-3-storage","read-only":false}' \
-device '{"driver":"ide-hd","bus":"ide.0","unit":0,"drive":"libvirt-3-storage","id":"ide0-0-0","bootindex":1}' \
-blockdev '{"driver":"file","filename":"/tmp/usbdisk.img","node-name":"libvirt-2-storage","read-only":false}' \
--device '{"driver":"usb-storage","bus":"usb.0","port":"1","drive":"libvirt-2-storage","id":"usb-disk0","removable":true}' \
+-device '{"driver":"usb-bot","id":"usb-disk0","bus":"usb.0","port":"1"}' \
+-device '{"bus":"usb-disk0.0","scsi-id":0,"lun":0,"driver":"scsi-hd","device_id":"drive-usb-disk0","drive":"libvirt-2-storage","id":"scsiusb-disk0","removable":true}' \
-blockdev '{"driver":"file","filename":"/tmp/scsidisk.img","node-name":"libvirt-1-storage","read-only":false}' \
-device '{"driver":"scsi-hd","bus":"scsi0.0","channel":0,"scsi-id":0,"lun":1,"device_id":"drive-scsi0-0-0-1","drive":"libvirt-1-storage","id":"scsi0-0-0-1","removable":true}' \
-audiodev '{"id":"audio1","driver":"none"}' \
diff --git a/tests/qemuxmlconfdata/disk-usb-device.x86_64-latest.args b/tests/qemuxmlconfdata/disk-usb-device.x86_64-latest.args
index 0fd7e755b1384227b63d6a080bd6af947596ae06..534780faf1a34af1a60dcca4dc71f91943267ea9 100644
--- a/tests/qemuxmlconfdata/disk-usb-device.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/disk-usb-device.x86_64-latest.args
@@ -30,7 +30,8 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-2-storage","read-only":false}' \
-device '{"driver":"ide-hd","bus":"ide.0","unit":0,"drive":"libvirt-2-storage","id":"ide0-0-0","bootindex":1}' \
-blockdev '{"driver":"file","filename":"/tmp/usbdisk.img","node-name":"libvirt-1-storage","read-only":false}' \
--device '{"driver":"usb-storage","bus":"usb.0","port":"1","drive":"libvirt-1-storage","id":"usb-disk0","removable":false}' \
+-device '{"driver":"usb-bot","id":"usb-disk0","bus":"usb.0","port":"1"}' \
+-device '{"bus":"usb-disk0.0","scsi-id":0,"lun":0,"driver":"scsi-hd","device_id":"drive-usb-disk0","drive":"libvirt-1-storage","id":"scsiusb-disk0"}' \
-audiodev '{"id":"audio1","driver":"none"}' \
-device '{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.0","addr":"0x2"}' \
-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
--
2.48.1On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: > usb-storage is a compound device that automatically creates a USB mass > storage device and a SCSI device as its backend. Unfortunately it lacks > some configuration options that are usually present with a SCSI device, > and cannot represent CD-ROM in particular. > > Replace usb-storage with usb-bot, which can be combined with a manually > created SCSI device. libvirt will configure the SCSI device in a way > identical with how QEMU does for usb-storage except that now it respects > a configuration option to represent CD-ROM. Is this change compatible for QEMU's VMState aka migration ABI compatible ? > > Resolves: https://gitlab.com/libvirt/libvirt/-/issues/368 > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com> > --- > src/qemu/qemu_alias.c | 3 +- > src/qemu/qemu_capabilities.c | 2 +- > src/qemu/qemu_command.c | 55 ++++++++++++++++++++-- > src/qemu/qemu_command.h | 5 ++ > src/qemu/qemu_hotplug.c | 34 ++++++++++--- > src/qemu/qemu_validate.c | 4 +- > tests/qemuhotplugtest.c | 8 +++- > .../qemuxmlconfdata/disk-cache.x86_64-latest.args | 3 +- > .../disk-cdrom-bus-other.x86_64-latest.args | 3 +- > .../disk-device-removable.x86_64-latest.args | 3 +- > .../disk-usb-device.x86_64-latest.args | 3 +- > 11 files changed, 102 insertions(+), 21 deletions(-) With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
On Mon, Mar 10, 2025 at 09:05:28 +0000, Daniel P. Berrangé wrote: > On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: > > usb-storage is a compound device that automatically creates a USB mass > > storage device and a SCSI device as its backend. Unfortunately it lacks > > some configuration options that are usually present with a SCSI device, > > and cannot represent CD-ROM in particular. > > > > Replace usb-storage with usb-bot, which can be combined with a manually > > created SCSI device. libvirt will configure the SCSI device in a way > > identical with how QEMU does for usb-storage except that now it respects > > a configuration option to represent CD-ROM. > > Is this change compatible for QEMU's VMState aka migration ABI compatible ? Based on my tests so far it seems compatible in terms of VMstate and also guest ABI at least to the first glance (lsusb, lsscsi -v etc) seems identical at least for the default 'read-write'/non-cdrom disk. I didn't yet test migrating with a cdrom to an older daemon though, which based on the above paragraph should have guest-visible difference.
On 2025/03/10 18:10, Peter Krempa wrote: > On Mon, Mar 10, 2025 at 09:05:28 +0000, Daniel P. Berrangé wrote: >> On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: >>> usb-storage is a compound device that automatically creates a USB mass >>> storage device and a SCSI device as its backend. Unfortunately it lacks >>> some configuration options that are usually present with a SCSI device, >>> and cannot represent CD-ROM in particular. >>> >>> Replace usb-storage with usb-bot, which can be combined with a manually >>> created SCSI device. libvirt will configure the SCSI device in a way >>> identical with how QEMU does for usb-storage except that now it respects >>> a configuration option to represent CD-ROM. >> >> Is this change compatible for QEMU's VMState aka migration ABI compatible ? > > Based on my tests so far it seems compatible in terms of VMstate and > also guest ABI at least to the first glance (lsusb, lsscsi -v etc) seems > identical at least for the default 'read-write'/non-cdrom disk. > > I didn't yet test migrating with a cdrom to an older daemon though, > which based on the above paragraph should have guest-visible difference. > It may work but QEMU doesn't guarantee that. Do you have a suggestion to deal with migration? We can keep using usb-storage for hard disk to avoid breaking, but for CD-ROM, we will need to revive the -drive option support (it was used instead of -blockdev and able to create a CD-ROM drive with usb-storage). Honestly I don't think anybody migrates a VM with a USB storage and I guess it's not worth keeping usb-storage and the -drive. Regards, Akihiko Odaki
On Mon, Mar 10, 2025 at 10:10:53AM +0100, Peter Krempa wrote: > On Mon, Mar 10, 2025 at 09:05:28 +0000, Daniel P. Berrangé wrote: > > On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: > > > usb-storage is a compound device that automatically creates a USB mass > > > storage device and a SCSI device as its backend. Unfortunately it lacks > > > some configuration options that are usually present with a SCSI device, > > > and cannot represent CD-ROM in particular. > > > > > > Replace usb-storage with usb-bot, which can be combined with a manually > > > created SCSI device. libvirt will configure the SCSI device in a way > > > identical with how QEMU does for usb-storage except that now it respects > > > a configuration option to represent CD-ROM. > > > > Is this change compatible for QEMU's VMState aka migration ABI compatible ? > > Based on my tests so far it seems compatible in terms of VMstate and > also guest ABI at least to the first glance (lsusb, lsscsi -v etc) seems > identical at least for the default 'read-write'/non-cdrom disk. > > I didn't yet test migrating with a cdrom to an older daemon though, > which based on the above paragraph should have guest-visible difference. Any such configuratin of the latter is arguably a bug though ? It was never presenting a cdrom, and that we allowed it was just a sign of missing XML validation surely ? With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
On Mon, Mar 10, 2025 at 09:13:11 +0000, Daniel P. Berrangé wrote: > On Mon, Mar 10, 2025 at 10:10:53AM +0100, Peter Krempa wrote: > > On Mon, Mar 10, 2025 at 09:05:28 +0000, Daniel P. Berrangé wrote: > > > On Sat, Mar 08, 2025 at 02:57:41PM +0900, Akihiko Odaki wrote: > > > > usb-storage is a compound device that automatically creates a USB mass > > > > storage device and a SCSI device as its backend. Unfortunately it lacks > > > > some configuration options that are usually present with a SCSI device, > > > > and cannot represent CD-ROM in particular. > > > > > > > > Replace usb-storage with usb-bot, which can be combined with a manually > > > > created SCSI device. libvirt will configure the SCSI device in a way > > > > identical with how QEMU does for usb-storage except that now it respects > > > > a configuration option to represent CD-ROM. > > > > > > Is this change compatible for QEMU's VMState aka migration ABI compatible ? > > > > Based on my tests so far it seems compatible in terms of VMstate and > > also guest ABI at least to the first glance (lsusb, lsscsi -v etc) seems > > identical at least for the default 'read-write'/non-cdrom disk. > > > > I didn't yet test migrating with a cdrom to an older daemon though, > > which based on the above paragraph should have guest-visible difference. > > Any such configuratin of the latter is arguably a bug though ? It was > never presenting a cdrom, and that we allowed it was just a sign of > missing XML validation surely ? Yes that could be the case. Although it is possible that it's even a regression from switching to blockdev as I've seen claims that usb cdrom did behave correctly at that point; but I didn't care to validate that for myself given how long ago it was that we switched to blockdev.
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