From e4f000025ac57ed4c731ffb0939f2e02bb84d856 Mon Sep 17 00:00:00 2001

Message-Id: <e4f000025ac57ed4c731ffb0939f2e02bb84d856@dist-git>

From: Jiri Denemark <jdenemar@redhat.com>

Date: Fri, 21 Jun 2019 09:26:11 +0200

Subject: [PATCH] qemu: Forbid MSR features with old QEMU

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Without "unavailable-features" CPU property we cannot properly detect

whether a specific MSR feature we asked for (either explicitly or

implicitly via a CPU model) was disabled by QEMU for some reason.

Because this could break migration, snapshots, and save/restore

operaions, it's better to just forbid any use of MSR features with QEMU

which lacks "unavailable-features" CPU property.

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

Reviewed-by: Ján Tomko <jtomko@redhat.com>

(cherry picked from commit 8eb4a89f5f7973f50aa8b6fa0b1a45b825dda208)

https://bugzilla.redhat.com/show_bug.cgi?id=1697627

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

Message-Id: <b077794613a01d8ebd69b27afef1ad2452a4810d.1561068591.git.jdenemar@redhat.com>

Reviewed-by: Ján Tomko <jtomko@redhat.com>

---

 src/qemu/qemu_process.c | 30 +++++++++++++++++++++++++++---

 1 file changed, 27 insertions(+), 3 deletions(-)

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

index d147e524ee..db14d322f5 100644

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

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

@@ -53,6 +53,7 @@

 #include "qemu_extdevice.h"

 #include "cpu/cpu.h"

+#include "cpu/cpu_x86.h"

 #include "datatypes.h"

 #include "virlog.h"

 #include "virerror.h"

@@ -5226,9 +5227,32 @@ qemuProcessStartValidate(virQEMUDriverPtr driver,

     if (qemuProcessStartValidateShmem(vm) < 0)

         return -1;

-    if (vm->def->cpu &&

-        virCPUValidateFeatures(vm->def->os.arch, vm->def->cpu) < 0)

-        return -1;

+    if (vm->def->cpu) {

+        if (virCPUValidateFeatures(vm->def->os.arch, vm->def->cpu) < 0)

+            return -1;

+

+        if (ARCH_IS_X86(vm->def->os.arch) &&

+            !virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_UNAVAILABLE_FEATURES)) {

+            VIR_AUTOSTRINGLIST features = NULL;

+            int n;

+

+            if ((n = virCPUDefCheckFeatures(vm->def->cpu,

+                                            virCPUx86FeatureFilterSelectMSR,

+                                            NULL,

+                                            &features)) < 0)

+                return -1;

+

+            if (n > 0) {

+                VIR_AUTOFREE(char *) str = NULL;

+

+                str = virStringListJoin((const char **)features, ", ");

+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,

+                               _("Some features cannot be reliably used "

+                                 "with this QEMU: %s"), str);

+                return -1;

+            }

+        }

+    }

     if (qemuProcessStartValidateDisks(vm, qemuCaps) < 0)

         return -1;

-- 

2.22.0