1. Patchew
  2. Libvirt
  3. [RFC PATCH 0/2] Handle physical address bits
  4. View patch

[RFC PATCH 2/2] qemu: Add support for max physical address size

Dario Faggioli posted 2 patches 4 years ago
There is a newer version of this series
[RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Dario Faggioli 4 years ago 
This patch maps /domain/cpu/maxphysaddr into -cpu parameters:

  - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
  - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42

Passthrough mode can only be used if the chosen CPU model is
'host-passthrough'.

The feature is available since QEMU 2.7.0.

Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
---
 src/qemu/qemu_capabilities.c                       |    2 +
 src/qemu/qemu_capabilities.h                       |    1 
 src/qemu/qemu_command.c                            |   28 ++++++++++++
 src/qemu/qemu_domain.c                             |   46 ++++++++++++++++++++
 tests/qemuxml2argvdata/cpu-phys-bits-emulate.args  |   29 +++++++++++++
 tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml   |   20 +++++++++
 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args |   30 +++++++++++++
 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml  |   20 +++++++++
 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err  |    1 
 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml  |   20 +++++++++
 .../cpu-phys-bits-passthrough.args                 |   29 +++++++++++++
 .../qemuxml2argvdata/cpu-phys-bits-passthrough.xml |   20 +++++++++
 .../cpu-phys-bits-passthrough2.err                 |    1 
 .../cpu-phys-bits-passthrough2.xml                 |   20 +++++++++
 .../cpu-phys-bits-passthrough3.err                 |    1 
 .../cpu-phys-bits-passthrough3.xml                 |   20 +++++++++
 tests/qemuxml2argvtest.c                           |    7 +++
 17 files changed, 295 insertions(+)
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
 create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index a67fb785b5..70adb423f1 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -603,6 +603,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
               "virtio-balloon.free-page-reporting",
               "block-export-add",
               "netdev.vhost-vdpa",
+              "host-phys-bits",
     );
 
 
@@ -1679,6 +1680,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsObjectPropsMaxCPU[] = {
     { "unavailable-features", QEMU_CAPS_CPU_UNAVAILABLE_FEATURES },
     { "kvm-no-adjvtime", QEMU_CAPS_CPU_KVM_NO_ADJVTIME },
     { "migratable", QEMU_CAPS_CPU_MIGRATABLE },
+    { "host-phys-bits", QEMU_CAPS_CPU_PHYS_BITS },
 };
 
 static virQEMUCapsObjectTypeProps virQEMUCapsObjectProps[] = {
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 047ba8a0ee..0fe97d2fd1 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -583,6 +583,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
     QEMU_CAPS_VIRTIO_BALLOON_FREE_PAGE_REPORTING, /*virtio balloon free-page-reporting */
     QEMU_CAPS_BLOCK_EXPORT_ADD, /* 'block-export-add' command is supported */
     QEMU_CAPS_NETDEV_VHOST_VDPA, /* -netdev vhost-vdpa*/
+    QEMU_CAPS_CPU_PHYS_BITS, /* -cpu phys-bits=42 or host-phys-bits=on */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 7847706594..d58f80547e 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6507,6 +6507,34 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
             virBufferAddLit(&buf, ",l3-cache=off");
     }
 
+    if (def->cpu && def->cpu->addr) {
+        virCPUMaxPhysAddrDefPtr addr = def->cpu->addr;
+
+        switch (addr->mode) {
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH:
+            if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_PHYS_BITS))
+               virBufferAddLit(&buf, ",host-phys-bits=on");
+            else
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("Setting host physical address bits is "
+                                 "not supported by this QEMU"));
+            break;
+
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE:
+            if (addr->bits != -1 &&
+                virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_PHYS_BITS))
+                virBufferAsprintf(&buf, ",phys-bits=%d", addr->bits);
+            else
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                               _("Physical address bits unspecified or "
+                                 "setting it not supported by this QEMU"));
+            break;
+
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_LAST:
+            break;
+        }
+    }
+
     cpu = virBufferContentAndReset(&cpu_buf);
     cpu_flags = virBufferContentAndReset(&buf);
 
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index d7dbca487a..e9f20d82a1 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -4051,6 +4051,52 @@ qemuDomainDefCPUPostParse(virDomainDefPtr def,
         }
     }
 
+    if (def->cpu->addr) {
+        virCPUMaxPhysAddrDefPtr addr = def->cpu->addr;
+
+        if (!ARCH_IS_X86(def->os.arch)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("CPU maximum physical address bits specification "
+                             "is not supported  for '%s' architecture"),
+                           virArchToString(def->os.arch));
+            return -1;
+        }
+
+        switch (addr->mode) {
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH:
+            if (def->cpu->mode != VIR_CPU_MODE_HOST_PASSTHROUGH) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("CPU maximum physical address bits mode '%s' "
+                                 "can only be used with '%s' CPUs"),
+                               virCPUMaxPhysAddrModeTypeToString(addr->mode),
+                               virCPUModeTypeToString(VIR_CPU_MODE_HOST_PASSTHROUGH));
+                return -1;
+            }
+            if (addr->bits != -1) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("CPU maximum physical address bits number "
+                                 "specification cannot be used with "
+                                 "mode='%s'"),
+                               virCPUMaxPhysAddrModeTypeToString(VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH));
+                return -1;
+            }
+            break;
+
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE:
+            if (addr->bits == -1) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("if using CPU maximum physical address "
+                                 "mode='%s', bits= must be specified too"),
+                               virCPUMaxPhysAddrModeTypeToString(VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE));
+                return -1;
+            }
+            break;
+
+        case VIR_CPU_MAX_PHYS_ADDR_MODE_LAST:
+            break;
+        }
+    }
+
     for (i = 0; i < def->cpu->nfeatures; i++) {
         virCPUFeatureDefPtr feature = &def->cpu->features[i];
 
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
new file mode 100644
index 0000000000..5627b41b25
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
@@ -0,0 +1,29 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-foo \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-machine pc,accel=kvm,usb=off,dump-guest-core=off \
+-cpu host,phys-bits=42 \
+-m 214 \
+-realtime mlock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
+nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
new file mode 100644
index 0000000000..f8bd63bc68
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <maxphysaddr mode='emulate' bits='42'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
new file mode 100644
index 0000000000..f105f96f02
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
@@ -0,0 +1,30 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-foo \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-machine pc,accel=kvm,usb=off,dump-guest-core=off \
+-cpu core2duo,+ds,+acpi,+ss,+ht,+tm,+pbe,+ds_cpl,+vmx,+est,+tm2,+cx16,+xtpr,\
++lahf_lm,phys-bits=42 \
+-m 214 \
+-realtime mlock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
+nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
new file mode 100644
index 0000000000..188b3066ed
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-model'>
+    <maxphysaddr bits='42' mode='emulate'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
new file mode 100644
index 0000000000..5e21998259
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
@@ -0,0 +1 @@
+unsupported configuration: if using CPU maximum physical address mode='emulate', bits= must be specified too
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
new file mode 100644
index 0000000000..30a14894dd
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <maxphysaddr mode='emulate'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
new file mode 100644
index 0000000000..a4f3f55bb9
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
@@ -0,0 +1,29 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-foo \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name foo \
+-S \
+-machine pc,accel=kvm,usb=off,dump-guest-core=off \
+-cpu host,host-phys-bits=on \
+-m 214 \
+-realtime mlock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
+nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-usb \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
new file mode 100644
index 0000000000..db570beb8d
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <maxphysaddr mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
new file mode 100644
index 0000000000..22009cc6e6
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
@@ -0,0 +1 @@
+unsupported configuration: CPU maximum physical address bits mode 'passthrough' can only be used with 'host-passthrough' CPUs
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
new file mode 100644
index 0000000000..511bbf9949
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-model'>
+    <maxphysaddr mode='passthrough'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
new file mode 100644
index 0000000000..28f2e43432
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
@@ -0,0 +1 @@
+unsupported configuration: CPU maximum physical address bits number specification cannot be used with mode='passthrough'
diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
new file mode 100644
index 0000000000..a94e567dcb
--- /dev/null
+++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
@@ -0,0 +1,20 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='host-passthrough'>
+    <maxphysaddr mode='passthrough' bits='42'/>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index c5a0095e0d..fd17fea744 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -3409,6 +3409,13 @@ mymain(void)
 
     DO_TEST_CAPS_LATEST("virtio-9p-multidevs");
 
+    DO_TEST("cpu-phys-bits-passthrough", QEMU_CAPS_KVM, QEMU_CAPS_CPU_PHYS_BITS);
+    DO_TEST("cpu-phys-bits-emulate", QEMU_CAPS_KVM, QEMU_CAPS_CPU_PHYS_BITS);
+    DO_TEST("cpu-phys-bits-emulate2", QEMU_CAPS_KVM, QEMU_CAPS_CPU_PHYS_BITS);
+    DO_TEST_PARSE_ERROR("cpu-phys-bits-emulate3", QEMU_CAPS_KVM);
+    DO_TEST_PARSE_ERROR("cpu-phys-bits-passthrough2", QEMU_CAPS_KVM);
+    DO_TEST_PARSE_ERROR("cpu-phys-bits-passthrough3", QEMU_CAPS_KVM);
+
     if (getenv("LIBVIRT_SKIP_CLEANUP") == NULL)
         virFileDeleteTree(fakerootdir);
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Christian Ehrhardt 4 years ago 
On Thu, Oct 29, 2020 at 5:07 PM Dario Faggioli <dfaggioli@suse.com> wrote:

> This patch maps /domain/cpu/maxphysaddr into -cpu parameters:
>
>   - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
>   - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42
>

I can't thank you enough Dario for starting this,
I have waited for this quite a while and never found the time for it myself
:-/

Looking at my todo notes I wondered if while touching it we should right
away also
add host-phys-bits-limit in the same spot?
See https://git.qemu.org/?p=qemu.git;a=commit;h=258fe08bd341d


> Passthrough mode can only be used if the chosen CPU model is
> 'host-passthrough'.
>
> The feature is available since QEMU 2.7.0.
>
> Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
> ---
>  src/qemu/qemu_capabilities.c                       |    2 +
>  src/qemu/qemu_capabilities.h                       |    1
>  src/qemu/qemu_command.c                            |   28 ++++++++++++
>  src/qemu/qemu_domain.c                             |   46
> ++++++++++++++++++++
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate.args  |   29 +++++++++++++
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml   |   20 +++++++++
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args |   30 +++++++++++++
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml  |   20 +++++++++
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err  |    1
>  tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml  |   20 +++++++++
>  .../cpu-phys-bits-passthrough.args                 |   29 +++++++++++++
>  .../qemuxml2argvdata/cpu-phys-bits-passthrough.xml |   20 +++++++++
>  .../cpu-phys-bits-passthrough2.err                 |    1
>  .../cpu-phys-bits-passthrough2.xml                 |   20 +++++++++
>  .../cpu-phys-bits-passthrough3.err                 |    1
>  .../cpu-phys-bits-passthrough3.xml                 |   20 +++++++++
>  tests/qemuxml2argvtest.c                           |    7 +++
>  17 files changed, 295 insertions(+)
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
>  create mode 100644 tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
>
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index a67fb785b5..70adb423f1 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -603,6 +603,7 @@ VIR_ENUM_IMPL(virQEMUCaps,
>                "virtio-balloon.free-page-reporting",
>                "block-export-add",
>                "netdev.vhost-vdpa",
> +              "host-phys-bits",
>      );
>
>
> @@ -1679,6 +1680,7 @@ static struct virQEMUCapsStringFlags
> virQEMUCapsObjectPropsMaxCPU[] = {
>      { "unavailable-features", QEMU_CAPS_CPU_UNAVAILABLE_FEATURES },
>      { "kvm-no-adjvtime", QEMU_CAPS_CPU_KVM_NO_ADJVTIME },
>      { "migratable", QEMU_CAPS_CPU_MIGRATABLE },
> +    { "host-phys-bits", QEMU_CAPS_CPU_PHYS_BITS },
>  };
>
>  static virQEMUCapsObjectTypeProps virQEMUCapsObjectProps[] = {
> diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
> index 047ba8a0ee..0fe97d2fd1 100644
> --- a/src/qemu/qemu_capabilities.h
> +++ b/src/qemu/qemu_capabilities.h
> @@ -583,6 +583,7 @@ typedef enum { /* virQEMUCapsFlags grouping marker for
> syntax-check */
>      QEMU_CAPS_VIRTIO_BALLOON_FREE_PAGE_REPORTING, /*virtio balloon
> free-page-reporting */
>      QEMU_CAPS_BLOCK_EXPORT_ADD, /* 'block-export-add' command is
> supported */
>      QEMU_CAPS_NETDEV_VHOST_VDPA, /* -netdev vhost-vdpa*/
> +    QEMU_CAPS_CPU_PHYS_BITS, /* -cpu phys-bits=42 or host-phys-bits=on */
>
>      QEMU_CAPS_LAST /* this must always be the last item */
>  } virQEMUCapsFlags;
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 7847706594..d58f80547e 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -6507,6 +6507,34 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
>              virBufferAddLit(&buf, ",l3-cache=off");
>      }
>
> +    if (def->cpu && def->cpu->addr) {
> +        virCPUMaxPhysAddrDefPtr addr = def->cpu->addr;
> +
> +        switch (addr->mode) {
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH:
> +            if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_PHYS_BITS))
> +               virBufferAddLit(&buf, ",host-phys-bits=on");
> +            else
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> +                               _("Setting host physical address bits is "
> +                                 "not supported by this QEMU"));
> +            break;
> +
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE:
> +            if (addr->bits != -1 &&
> +                virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_PHYS_BITS))
> +                virBufferAsprintf(&buf, ",phys-bits=%d", addr->bits);
> +            else
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> +                               _("Physical address bits unspecified or "
> +                                 "setting it not supported by this
> QEMU"));
> +            break;
> +
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_LAST:
> +            break;
> +        }
> +    }
> +
>      cpu = virBufferContentAndReset(&cpu_buf);
>      cpu_flags = virBufferContentAndReset(&buf);
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index d7dbca487a..e9f20d82a1 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -4051,6 +4051,52 @@ qemuDomainDefCPUPostParse(virDomainDefPtr def,
>          }
>      }
>
> +    if (def->cpu->addr) {
> +        virCPUMaxPhysAddrDefPtr addr = def->cpu->addr;
> +
> +        if (!ARCH_IS_X86(def->os.arch)) {
> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                           _("CPU maximum physical address bits
> specification "
> +                             "is not supported  for '%s' architecture"),
> +                           virArchToString(def->os.arch));
> +            return -1;
> +        }
> +
> +        switch (addr->mode) {
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH:
> +            if (def->cpu->mode != VIR_CPU_MODE_HOST_PASSTHROUGH) {
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                               _("CPU maximum physical address bits mode
> '%s' "
> +                                 "can only be used with '%s' CPUs"),
> +
>  virCPUMaxPhysAddrModeTypeToString(addr->mode),
> +
>  virCPUModeTypeToString(VIR_CPU_MODE_HOST_PASSTHROUGH));
> +                return -1;
> +            }
> +            if (addr->bits != -1) {
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                               _("CPU maximum physical address bits
> number "
> +                                 "specification cannot be used with "
> +                                 "mode='%s'"),
> +
>  virCPUMaxPhysAddrModeTypeToString(VIR_CPU_MAX_PHYS_ADDR_MODE_PASSTHROUGH));
> +                return -1;
> +            }
> +            break;
> +
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE:
> +            if (addr->bits == -1) {
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                               _("if using CPU maximum physical address "
> +                                 "mode='%s', bits= must be specified
> too"),
> +
>  virCPUMaxPhysAddrModeTypeToString(VIR_CPU_MAX_PHYS_ADDR_MODE_EMULATE));
> +                return -1;
> +            }
> +            break;
> +
> +        case VIR_CPU_MAX_PHYS_ADDR_MODE_LAST:
> +            break;
> +        }
> +    }
> +
>      for (i = 0; i < def->cpu->nfeatures; i++) {
>          virCPUFeatureDefPtr feature = &def->cpu->features[i];
>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
> new file mode 100644
> index 0000000000..5627b41b25
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.args
> @@ -0,0 +1,29 @@
> +LC_ALL=C \
> +PATH=/bin \
> +HOME=/tmp/lib/domain--1-foo \
> +USER=test \
> +LOGNAME=test \
> +XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
> +XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
> +XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
> +QEMU_AUDIO_DRV=none \
> +/usr/bin/qemu-system-x86_64 \
> +-name foo \
> +-S \
> +-machine pc,accel=kvm,usb=off,dump-guest-core=off \
> +-cpu host,phys-bits=42 \
> +-m 214 \
> +-realtime mlock=off \
> +-smp 1,sockets=1,cores=1,threads=1 \
> +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
> +-display none \
> +-no-user-config \
> +-nodefaults \
> +-chardev
> socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
> +nowait \
> +-mon chardev=charmonitor,id=monitor,mode=control \
> +-rtc base=utc \
> +-no-shutdown \
> +-no-acpi \
> +-usb \
> +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
> new file mode 100644
> index 0000000000..f8bd63bc68
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-passthrough'>
> +    <maxphysaddr mode='emulate' bits='42'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
> new file mode 100644
> index 0000000000..f105f96f02
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.args
> @@ -0,0 +1,30 @@
> +LC_ALL=C \
> +PATH=/bin \
> +HOME=/tmp/lib/domain--1-foo \
> +USER=test \
> +LOGNAME=test \
> +XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
> +XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
> +XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
> +QEMU_AUDIO_DRV=none \
> +/usr/bin/qemu-system-x86_64 \
> +-name foo \
> +-S \
> +-machine pc,accel=kvm,usb=off,dump-guest-core=off \
> +-cpu
> core2duo,+ds,+acpi,+ss,+ht,+tm,+pbe,+ds_cpl,+vmx,+est,+tm2,+cx16,+xtpr,\
> ++lahf_lm,phys-bits=42 \
> +-m 214 \
> +-realtime mlock=off \
> +-smp 1,sockets=1,cores=1,threads=1 \
> +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
> +-display none \
> +-no-user-config \
> +-nodefaults \
> +-chardev
> socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
> +nowait \
> +-mon chardev=charmonitor,id=monitor,mode=control \
> +-rtc base=utc \
> +-no-shutdown \
> +-no-acpi \
> +-usb \
> +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
> new file mode 100644
> index 0000000000..188b3066ed
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate2.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-model'>
> +    <maxphysaddr bits='42' mode='emulate'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
> new file mode 100644
> index 0000000000..5e21998259
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.err
> @@ -0,0 +1 @@
> +unsupported configuration: if using CPU maximum physical address
> mode='emulate', bits= must be specified too
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
> new file mode 100644
> index 0000000000..30a14894dd
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-emulate3.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-passthrough'>
> +    <maxphysaddr mode='emulate'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
> new file mode 100644
> index 0000000000..a4f3f55bb9
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.args
> @@ -0,0 +1,29 @@
> +LC_ALL=C \
> +PATH=/bin \
> +HOME=/tmp/lib/domain--1-foo \
> +USER=test \
> +LOGNAME=test \
> +XDG_DATA_HOME=/tmp/lib/domain--1-foo/.local/share \
> +XDG_CACHE_HOME=/tmp/lib/domain--1-foo/.cache \
> +XDG_CONFIG_HOME=/tmp/lib/domain--1-foo/.config \
> +QEMU_AUDIO_DRV=none \
> +/usr/bin/qemu-system-x86_64 \
> +-name foo \
> +-S \
> +-machine pc,accel=kvm,usb=off,dump-guest-core=off \
> +-cpu host,host-phys-bits=on \
> +-m 214 \
> +-realtime mlock=off \
> +-smp 1,sockets=1,cores=1,threads=1 \
> +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
> +-display none \
> +-no-user-config \
> +-nodefaults \
> +-chardev
> socket,id=charmonitor,path=/tmp/lib/domain--1-foo/monitor.sock,server,\
> +nowait \
> +-mon chardev=charmonitor,id=monitor,mode=control \
> +-rtc base=utc \
> +-no-shutdown \
> +-no-acpi \
> +-usb \
> +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
> new file mode 100644
> index 0000000000..db570beb8d
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-passthrough'>
> +    <maxphysaddr mode='passthrough'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
> new file mode 100644
> index 0000000000..22009cc6e6
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.err
> @@ -0,0 +1 @@
> +unsupported configuration: CPU maximum physical address bits mode
> 'passthrough' can only be used with 'host-passthrough' CPUs
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
> new file mode 100644
> index 0000000000..511bbf9949
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough2.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-model'>
> +    <maxphysaddr mode='passthrough'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
> new file mode 100644
> index 0000000000..28f2e43432
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.err
> @@ -0,0 +1 @@
> +unsupported configuration: CPU maximum physical address bits number
> specification cannot be used with mode='passthrough'
> diff --git a/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
> b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
> new file mode 100644
> index 0000000000..a94e567dcb
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/cpu-phys-bits-passthrough3.xml
> @@ -0,0 +1,20 @@
> +<domain type='kvm'>
> +  <name>foo</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory unit='KiB'>219136</memory>
> +  <currentMemory unit='KiB'>219136</currentMemory>
> +  <vcpu placement='static'>1</vcpu>
> +  <os>
> +    <type arch='x86_64' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <cpu mode='host-passthrough'>
> +    <maxphysaddr mode='passthrough' bits='42'/>
> +  </cpu>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index c5a0095e0d..fd17fea744 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -3409,6 +3409,13 @@ mymain(void)
>
>      DO_TEST_CAPS_LATEST("virtio-9p-multidevs");
>
> +    DO_TEST("cpu-phys-bits-passthrough", QEMU_CAPS_KVM,
> QEMU_CAPS_CPU_PHYS_BITS);
> +    DO_TEST("cpu-phys-bits-emulate", QEMU_CAPS_KVM,
> QEMU_CAPS_CPU_PHYS_BITS);
> +    DO_TEST("cpu-phys-bits-emulate2", QEMU_CAPS_KVM,
> QEMU_CAPS_CPU_PHYS_BITS);
> +    DO_TEST_PARSE_ERROR("cpu-phys-bits-emulate3", QEMU_CAPS_KVM);
> +    DO_TEST_PARSE_ERROR("cpu-phys-bits-passthrough2", QEMU_CAPS_KVM);
> +    DO_TEST_PARSE_ERROR("cpu-phys-bits-passthrough3", QEMU_CAPS_KVM);
> +
>      if (getenv("LIBVIRT_SKIP_CLEANUP") == NULL)
>          virFileDeleteTree(fakerootdir);
>
>
>
>

-- 
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Daniel P. Berrangé 4 years ago 
On Mon, Nov 02, 2020 at 09:14:22AM +0100, Christian Ehrhardt wrote:
> On Thu, Oct 29, 2020 at 5:07 PM Dario Faggioli <dfaggioli@suse.com> wrote:
> 
> > This patch maps /domain/cpu/maxphysaddr into -cpu parameters:
> >
> >   - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
> >   - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42
> >
> 
> I can't thank you enough Dario for starting this,
> I have waited for this quite a while and never found the time for it myself
> :-/
> 
> Looking at my todo notes I wondered if while touching it we should right
> away also
> add host-phys-bits-limit in the same spot?
> See https://git.qemu.org/?p=qemu.git;a=commit;h=258fe08bd341d

I'm not convinced we actally need it in libvirt. Assuming we report the
host phys bits in the capabilities XML, apps can already achieve this
functionality with the mode=emulate bits=NN settings  by populating NN
based on the capabilities XML.


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 :|
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Dario Faggioli 4 years ago 
On Wed, 2020-11-04 at 13:11 +0000, Daniel P. Berrangé wrote:
> On Mon, Nov 02, 2020 at 09:14:22AM +0100, Christian Ehrhardt wrote:
> > 
> > Looking at my todo notes I wondered if while touching it we should
> > right
> > away also
> > add host-phys-bits-limit in the same spot?
> > See https://git.qemu.org/?p=qemu.git;a=commit;h=258fe08bd341d
> 
> I'm not convinced we actally need it in libvirt. Assuming we report
> the
> host phys bits in the capabilities XML, apps can already achieve this
> functionality with the mode=emulate bits=NN settings  by populating
> NN
> based on the capabilities XML.
> 
Right. So, host-phys-bits-limit seems to exist because:
"Some downstream distributions of QEMU set host-phys-bits=on by
default. [...] Now choosing a large phys-bits value for a VM has bigger
impact: it will make KVM use 5-level EPT even when it's not really
necessary."

And we want to be able to, from QEMU: "keep using the host phys-bits
value, but only if it's smaller than 48."

So, I was thinking that, in a world where QEMU will
have host-phys-bits=on by default, if using `-cpu host` you may want to
be able to do the same from libvirt, i.e., "same as host, but not more
than NN".

In my head (and drafts), that would happen with:

<maxphysaddr mode="passthrough" limit="NN"/>   (1)

Which is very similar and may be identical to:

<maxphysaddr mode="emulate" bits="NN"/>        (2)

Whether or not they're actually identical, e.g., if NN > MM, depends on
what QEMU does. In that case, with (1) we set  MM. With (2), if QEMU
let us do that, we set NN. (And when I say what QEMU does, I don't
mean, right know, I mean in the particular version in use, assuming
that at least in theory it can change between different versions).

So, maybe having (1) may be the only way of making sure that I get
min(NN,MM), irrespective of QEMU version/behavior. Or am I missing
something?

That's why I happen to think there could be value in having limit... Or
does this all just not make sense? :-)

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Daniel P. Berrangé 4 years ago 
On Wed, Nov 04, 2020 at 07:00:16PM +0100, Dario Faggioli wrote:
> On Wed, 2020-11-04 at 13:11 +0000, Daniel P. Berrangé wrote:
> > On Mon, Nov 02, 2020 at 09:14:22AM +0100, Christian Ehrhardt wrote:
> > > 
> > > Looking at my todo notes I wondered if while touching it we should
> > > right
> > > away also
> > > add host-phys-bits-limit in the same spot?
> > > See https://git.qemu.org/?p=qemu.git;a=commit;h=258fe08bd341d
> > 
> > I'm not convinced we actally need it in libvirt. Assuming we report
> > the
> > host phys bits in the capabilities XML, apps can already achieve this
> > functionality with the mode=emulate bits=NN settings  by populating
> > NN
> > based on the capabilities XML.
> > 
> Right. So, host-phys-bits-limit seems to exist because:
> "Some downstream distributions of QEMU set host-phys-bits=on by
> default. [...] Now choosing a large phys-bits value for a VM has bigger
> impact: it will make KVM use 5-level EPT even when it's not really
> necessary."
> 
> And we want to be able to, from QEMU: "keep using the host phys-bits
> value, but only if it's smaller than 48."

Right so it is basically a hack to workaround problem with historical
defaults in QEMU. In the libvirt case we're not dealing with defaults,
we have explicit XML element to express what we want. So we can express
it straight away and not need this hack.

> 
> So, I was thinking that, in a world where QEMU will
> have host-phys-bits=on by default, if using `-cpu host` you may want to
> be able to do the same from libvirt, i.e., "same as host, but not more
> than NN".
> 
> In my head (and drafts), that would happen with:
> 
> <maxphysaddr mode="passthrough" limit="NN"/>   (1)
> 
> Which is very similar and may be identical to:
> 
> <maxphysaddr mode="emulate" bits="NN"/>        (2)
> 
> Whether or not they're actually identical, e.g., if NN > MM, depends on
> what QEMU does. In that case, with (1) we set  MM. With (2), if QEMU
> let us do that, we set NN. (And when I say what QEMU does, I don't
> mean, right know, I mean in the particular version in use, assuming
> that at least in theory it can change between different versions).
> 
> So, maybe having (1) may be the only way of making sure that I get
> min(NN,MM), irrespective of QEMU version/behavior. Or am I missing
> something?

I don't see any functional difference between 1 & 2 from libvirt's
side. In fact (2) is probably better because it can work on any version
of QEMU, even before host-phys-bits-limit was introduced.

The "downside" is that an app has to read the capabilities to see the
current host limit and choose the "NN" value.

> That's why I happen to think there could be value in having limit... Or
> does this all just not make sense? :-)

I think we can ignore  host-phys-bits-limit. If it later turns out we
really do need it, we can add it to libvirt, but until then pretend
it doesn't exist.

> 
> Thanks and Regards
> -- 
> Dario Faggioli, Ph.D
> http://about.me/dario.faggioli
> Virtualization Software Engineer
> SUSE Labs, SUSE https://www.suse.com/
> -------------------------------------------------------------------
> <<This happens because _I_ choose it to happen!>> (Raistlin Majere)



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 :|
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Dario Faggioli 4 years ago 
On Wed, 2020-11-04 at 18:04 +0000, Daniel P. Berrangé wrote:
> On Wed, Nov 04, 2020 at 07:00:16PM +0100, Dario Faggioli wrote:
> > > 
> > Right. So, host-phys-bits-limit seems to exist because:
> > "Some downstream distributions of QEMU set host-phys-bits=on by
> > default. [...] Now choosing a large phys-bits value for a VM has
> > bigger
> > impact: it will make KVM use 5-level EPT even when it's not really
> > necessary."
> > 
> > And we want to be able to, from QEMU: "keep using the host phys-
> > bits
> > value, but only if it's smaller than 48."
> 
> Right so it is basically a hack to workaround problem with historical
> defaults in QEMU. In the libvirt case we're not dealing with
> defaults,
> we have explicit XML element to express what we want. So we can
> express
> it straight away and not need this hack.
> 
Ok.
> 

> > In my head (and drafts), that would happen with:
> > 
> > <maxphysaddr mode="passthrough" limit="NN"/>   (1)
> > 
> > Which is very similar and may be identical to:
> > 
> > <maxphysaddr mode="emulate" bits="NN"/>        (2)
> > 
> > [...]
> >
> > So, maybe having (1) may be the only way of making sure that I get
> > min(NN,MM), irrespective of QEMU version/behavior. Or am I missing
> > something?
> 
> I don't see any functional difference between 1 & 2 from libvirt's
> side. In fact (2) is probably better because it can work on any
> version
> of QEMU, even before host-phys-bits-limit was introduced.
> 
That is indeed true.

> The "downside" is that an app has to read the capabilities to see the
> current host limit and choose the "NN" value.
> 
> > That's why I happen to think there could be value in having
> > limit... Or
> > does this all just not make sense? :-)
> 
> I think we can ignore  host-phys-bits-limit. If it later turns out we
> really do need it, we can add it to libvirt, but until then pretend
> it doesn't exist.
> 
Right. I think I've understood your line of reasoning and I agree.
Especially on the fact that we can ignore it for now, and always add it
later, if we see the need for it.

And I certainly can look into adding the phys bits to the host
capabilities.

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Dario Faggioli 4 years ago 
On Mon, 2020-11-02 at 09:14 +0100, Christian Ehrhardt wrote:
> 
> On Thu, Oct 29, 2020 at 5:07 PM Dario Faggioli <dfaggioli@suse.com>
> wrote:
> > This patch maps /domain/cpu/maxphysaddr into -cpu parameters:
> > 
> >   - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
> >   - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42
> > 
> 
> I can't thank you enough Dario for starting this,
> I have waited for this quite a while and never found the time for it
> myself :-/
>
Hi!

Yeah, it was sitting in my TODO list for a little while as well.

Then I decided to mention that I'd do it in my talk at KVM Forum...
Which is usually a pretty good push for actually do it! ;-P
> 
> Looking at my todo notes I wondered if while touching it we should
> right away also
> add host-phys-bits-limit in the same spot?
> See https://git.qemu.org/?p=qemu.git;a=commit;h=258fe08bd341d
>  
Yes, I'm aware of it, and it looks easy to support.

And I agree that we can do it contextually.

I even have it in drafted patches, but I decided to fire these out as
early as possible, to capture some early feedback.

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Daniel P. Berrangé 4 years ago 
On Thu, Oct 29, 2020 at 03:55:42PM +0000, Dario Faggioli wrote:
> This patch maps /domain/cpu/maxphysaddr into -cpu parameters:
> 
>   - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
>   - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42
> 
> Passthrough mode can only be used if the chosen CPU model is
> 'host-passthrough'.
> 
> The feature is available since QEMU 2.7.0.

I wonder if we need to care about doing any kind of host compatibility
checking when these are specified.

QEMU historically hasn't checked compatibility, meaning you could
configure bits=48 on a host CPU that only supports bits=40. Things
would seem to work unless you gave a guest RAM size that needed
soo many bits.

QEMU is reluctant to change things due to back compat issues with
existing deployments. Libvirt wouldn't have that issue though, as
we would only need to enforce it when users actually gave the
<maxphysaddr> element, which is opt-in and won't be present in
existing guests.


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 :|
Re: [RFC PATCH 2/2] qemu: Add support for max physical address size
Posted by Dario Faggioli 4 years ago 
On Wed, 2020-11-04 at 13:14 +0000, Daniel P. Berrangé wrote:
> On Thu, Oct 29, 2020 at 03:55:42PM +0000, Dario Faggioli wrote:
> > This patch maps /domain/cpu/maxphysaddr into -cpu parameters:
> > 
> >   - <maxphysaddr mode='passthrough'/> becomes host-phys-bits=on
> >   - <maxphysaddr mode='emualte' bits='42'/> becomes phys-bits=42
> > 
> > Passthrough mode can only be used if the chosen CPU model is
> > 'host-passthrough'.
> > 
> > The feature is available since QEMU 2.7.0.
> 
> I wonder if we need to care about doing any kind of host
> compatibility
> checking when these are specified.
> 
Ah, yes, this is a good point.

> QEMU is reluctant to change things due to back compat issues with
> existing deployments. Libvirt wouldn't have that issue though, as
> we would only need to enforce it when users actually gave the
> <maxphysaddr> element, which is opt-in and won't be present in
> existing guests.
> 
Yes, and I'm already adding the logic for checking the host phys bits,
for putting it in the host capabilities, so it should be easy enough to
add a check here.

I'll go for it.

Thanks and Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
-------------------------------------------------------------------
<<This happens because _I_ choose it to happen!>> (Raistlin Majere)

Patchew 2.1-devel-b67e4c2

© 2016 - 2024 Red Hat, Inc.