From b2196db320485b642d6654279ebb6b75eeafd3e9 Mon Sep 17 00:00:00 2001

Message-Id: <b2196db320485b642d6654279ebb6b75eeafd3e9@dist-git>

From: Jiri Denemark <jdenemar@redhat.com>

Date: Tue, 11 Apr 2017 20:46:05 +0200

Subject: [PATCH] qemu: Use more data for comparing CPUs

With QEMU older than 2.9.0 libvirt uses CPUID instruction to determine

what CPU features are supported on the host. This was later used when

checking compatibility of guest CPUs. Since QEMU 2.9.0 we ask QEMU for

the host CPU data. But the two methods we use usually provide disjoint

sets of CPU features because QEMU/KVM does not support all features

provided by the host CPU and on the other hand it can enable some

feature even if the host CPU does not support them.

So if there is a domain which requires a CPU features disabled by

QEMU/KVM, libvirt will refuse to start it with QEMU > 2.9.0 as its guest

CPU is incompatible with the host CPU data we got from QEMU. But such

domain would happily start on older QEMU (of course, the features would

be missing the guest CPU). To fix this regression, we need to combine

both CPU feature sets when checking guest CPU compatibility.

https://bugzilla.redhat.com/show_bug.cgi?id=1439933

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

(cherry picked from commit 5b4a6adb5ca24a6cb91cdc55c31506fb278d3a91)

https://bugzilla.redhat.com/show_bug.cgi?id=1444421

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

---

 src/qemu/qemu_capabilities.c | 35 +++++++++++++++++++++++++++++++++--

 src/qemu/qemu_capabilities.h |  4 ++++

 src/qemu/qemu_process.c      |  2 +-

 3 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c

index ec773971e..49de506ed 100644

--- a/src/qemu/qemu_capabilities.c

+++ b/src/qemu/qemu_capabilities.c

@@ -387,6 +387,10 @@ struct _virQEMUCapsHostCPUData {

     virCPUDefPtr reported;

     /* Migratable host CPU definition used for updating guest CPU. */

     virCPUDefPtr migratable;

+    /* CPU definition with features detected by libvirt using virCPUGetHost

+     * combined with features reported by QEMU. This is used for backward

+     * compatible comparison between a guest CPU and a host CPU. */

+    virCPUDefPtr full;

 };

 /*

@@ -2112,6 +2116,10 @@ virQEMUCapsHostCPUDataCopy(virQEMUCapsHostCPUDataPtr dst,

         !(dst->migratable = virCPUDefCopy(src->migratable)))

         return -1;

+    if (src->full &&

+        !(dst->full = virCPUDefCopy(src->full)))

+        return -1;

+

     return 0;

 }

@@ -2122,6 +2130,7 @@ virQEMUCapsHostCPUDataClear(virQEMUCapsHostCPUDataPtr cpuData)

     qemuMonitorCPUModelInfoFree(cpuData->info);

     virCPUDefFree(cpuData->reported);

     virCPUDefFree(cpuData->migratable);

+    virCPUDefFree(cpuData->full);

     memset(cpuData, 0, sizeof(*cpuData));

 }

@@ -2463,6 +2472,11 @@ virQEMUCapsGetHostModel(virQEMUCapsPtr qemuCaps,

     case VIR_QEMU_CAPS_HOST_CPU_MIGRATABLE:

         return cpuData->migratable;

+

+    case VIR_QEMU_CAPS_HOST_CPU_FULL:

+        /* 'full' is non-NULL only if we have data from both QEMU and

+         * virCPUGetHost */

+        return cpuData->full ? cpuData->full : cpuData->reported;

     }

     return NULL;

@@ -2473,12 +2487,14 @@ static void

 virQEMUCapsSetHostModel(virQEMUCapsPtr qemuCaps,

                         virDomainVirtType type,

                         virCPUDefPtr reported,

-                        virCPUDefPtr migratable)

+                        virCPUDefPtr migratable,

+                        virCPUDefPtr full)

 {

     virQEMUCapsHostCPUDataPtr cpuData = virQEMUCapsGetHostCPUData(qemuCaps, type);

     cpuData->reported = reported;

     cpuData->migratable = migratable;

+    cpuData->full = full;

 }

@@ -3350,6 +3366,8 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,

     virCPUDefPtr cpu = NULL;

     virCPUDefPtr migCPU = NULL;

     virCPUDefPtr hostCPU = NULL;

+    virCPUDefPtr fullCPU = NULL;

+    size_t i;

     int rc;

     if (!caps || !virQEMUCapsGuestIsNative(caps->host.arch, qemuCaps->arch))

@@ -3369,6 +3387,18 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,

                                      virQEMUCapsCPUFilterFeatures,

                                      qemuCaps) < 0)

             goto error;

+    } else if (type == VIR_DOMAIN_VIRT_KVM &&

+               virCPUGetHostIsSupported(qemuCaps->arch)) {

+        if (!(fullCPU = virCPUGetHost(qemuCaps->arch, VIR_CPU_TYPE_GUEST,

+                                      NULL, NULL, 0)))

+            goto error;

+

+        for (i = 0; i < cpu->nfeatures; i++) {

+            if (cpu->features[i].policy == VIR_CPU_FEATURE_REQUIRE &&

+                virCPUDefUpdateFeature(fullCPU, cpu->features[i].name,

+                                       VIR_CPU_FEATURE_REQUIRE) < 0)

+                goto error;

+        }

     }

     if (!(migCPU = virQEMUCapsNewHostCPUModel()))

@@ -3384,7 +3414,7 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,

             goto error;

     }

-    virQEMUCapsSetHostModel(qemuCaps, type, cpu, migCPU);

+    virQEMUCapsSetHostModel(qemuCaps, type, cpu, migCPU, fullCPU);

  cleanup:

     virCPUDefFree(hostCPU);

@@ -3393,6 +3423,7 @@ virQEMUCapsInitHostCPUModel(virQEMUCapsPtr qemuCaps,

  error:

     virCPUDefFree(cpu);

     virCPUDefFree(migCPU);

+    virCPUDefFree(fullCPU);

     virResetLastError();

     goto cleanup;

 }

diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h

index 16fe044cc..644b8e27b 100644

--- a/src/qemu/qemu_capabilities.h

+++ b/src/qemu/qemu_capabilities.h

@@ -456,6 +456,10 @@ typedef enum {

     VIR_QEMU_CAPS_HOST_CPU_REPORTED,

     /* Migratable host CPU definition used for updating guest CPU. */

     VIR_QEMU_CAPS_HOST_CPU_MIGRATABLE,

+    /* CPU definition with features detected by libvirt using virCPUGetHost

+     * combined with features reported by QEMU. This is used for backward

+     * compatible comparison between a guest CPU and a host CPU. */

+    VIR_QEMU_CAPS_HOST_CPU_FULL,

 } virQEMUCapsHostCPUType;

 virCPUDefPtr virQEMUCapsGetHostModel(virQEMUCapsPtr qemuCaps,

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c

index c81389ef2..a33ec87e6 100644

--- a/src/qemu/qemu_process.c

+++ b/src/qemu/qemu_process.c

@@ -5307,7 +5307,7 @@ qemuProcessUpdateGuestCPU(virDomainDefPtr def,

     if (def->cpu->check == VIR_CPU_CHECK_PARTIAL &&

         virCPUCompare(caps->host.arch,

                       virQEMUCapsGetHostModel(qemuCaps, def->virtType,

-                                              VIR_QEMU_CAPS_HOST_CPU_REPORTED),

+                                              VIR_QEMU_CAPS_HOST_CPU_FULL),

                       def->cpu, true) < 0)

         return -1;

-- 

2.12.2