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qemu: Fix migration with disabled vmx-* CPU features

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When starting a domain on a host which lacks a vmx-* CPU feature which
is expected to be enabled by the CPU model specified in the domain XML,
libvirt properly marks such feature as disabled in the active domain
XML. But migrating the domain to a similar host which lacks the same
vmx-* feature will fail with libvirt reporting the feature as missing.
This is because of a bug in the hack ensuring backward compatibility
libvirt running on the destination thinks the missing feature is
expected to be enabled.

https://issues.redhat.com/browse/RHEL-40899

Fixes: v10.1.0-85-g5fbfa5ab8a
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
This commit is contained in:
Jiri Denemark 2024-06-12 16:44:28 +02:00
parent ba6cd2d5a8
commit e622970c87
1 changed files with 27 additions and 17 deletions
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44
src/cpu/cpu_x86.c
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@ -3021,10 +3021,7 @@ virCPUx86UpdateLive(virCPUDef *cpu,
if (!(map = virCPUx86GetMap()))
return -1;
if (!(model = x86ModelFromCPU(cpu, map, -1)))
return -1;
if (hostPassthrough &&
if (!(model = x86ModelFromCPU(cpu, map, -1)) ||
!(modelDisabled = x86ModelFromCPU(cpu, map, VIR_CPU_FEATURE_DISABLE)))
return -1;
@ -3037,12 +3034,19 @@ virCPUx86UpdateLive(virCPUDef *cpu,
for (i = 0; i < map->nfeatures; i++) {
virCPUx86Feature *feature = map->features[i];
virCPUFeaturePolicy expected = VIR_CPU_FEATURE_LAST;
bool explicit = false;
bool ignore = false;
if (x86DataIsSubset(&model->data, &feature->data))
if (x86DataIsSubset(&model->data, &feature->data)) {
explicit = true;
expected = VIR_CPU_FEATURE_REQUIRE;
else if (!hostPassthrough ||
x86DataIsSubset(&modelDisabled->data, &feature->data))
} else if (x86DataIsSubset(&modelDisabled->data, &feature->data)) {
explicit = true;
expected = VIR_CPU_FEATURE_DISABLE;
} else if (!hostPassthrough) {
/* implicitly disabled */
expected = VIR_CPU_FEATURE_DISABLE;
}
if (x86DataIsSubset(&enabled, &feature->data) &&
x86DataIsSubset(&disabled, &feature->data)) {
@ -3052,30 +3056,36 @@ virCPUx86UpdateLive(virCPUDef *cpu,
return -1;
}
/* Features enabled or disabled by the hypervisor are ignored by
* check='full' in case they were added to the model later and not
* explicitly mentioned in the CPU definition. This matches how libvirt
* behaved before the features were added.
*/
if (!explicit &&
g_strv_contains((const char **) model->addedFeatures, feature->name))
ignore = true;
if (expected == VIR_CPU_FEATURE_DISABLE &&
x86DataIsSubset(&enabled, &feature->data)) {
VIR_DEBUG("Feature '%s' enabled by the hypervisor", feature->name);
/* Extra features enabled by the hypervisor are ignored by
* check='full' in case they were added to the model later for
* backward compatibility with the older definition of the model.
*/
if (cpu->check == VIR_CPU_CHECK_FULL &&
!g_strv_contains((const char **) model->addedFeatures, feature->name)) {
if (cpu->check == VIR_CPU_CHECK_FULL && !ignore)
virBufferAsprintf(&bufAdded, "%s,", feature->name);
} else {
else
virCPUDefUpdateFeature(cpu, feature->name, VIR_CPU_FEATURE_REQUIRE);
}
}
if (x86DataIsSubset(&disabled, &feature->data) ||
(expected == VIR_CPU_FEATURE_REQUIRE &&
!x86DataIsSubset(&enabled, &feature->data))) {
VIR_DEBUG("Feature '%s' disabled by the hypervisor", feature->name);
if (cpu->check == VIR_CPU_CHECK_FULL)
if (cpu->check == VIR_CPU_CHECK_FULL && !ignore) {
virBufferAsprintf(&bufRemoved, "%s,", feature->name);
else
} else {
virCPUDefUpdateFeature(cpu, feature->name, VIR_CPU_FEATURE_DISABLE);
x86DataSubtract(&disabled, &feature->data);
}
}
}