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From e4f000025ac57ed4c731ffb0939f2e02bb84d856 Mon Sep 17 00:00:00 2001
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Message-Id: <e4f000025ac57ed4c731ffb0939f2e02bb84d856@dist-git>
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From: Jiri Denemark <jdenemar@redhat.com>
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Date: Fri, 21 Jun 2019 09:26:11 +0200
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Subject: [PATCH] qemu: Forbid MSR features with old QEMU
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Without "unavailable-features" CPU property we cannot properly detect
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whether a specific MSR feature we asked for (either explicitly or
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implicitly via a CPU model) was disabled by QEMU for some reason.
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Because this could break migration, snapshots, and save/restore
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operaions, it's better to just forbid any use of MSR features with QEMU
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which lacks "unavailable-features" CPU property.
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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(cherry picked from commit 8eb4a89f5f7973f50aa8b6fa0b1a45b825dda208)
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https://bugzilla.redhat.com/show_bug.cgi?id=1697627
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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Message-Id: <b077794613a01d8ebd69b27afef1ad2452a4810d.1561068591.git.jdenemar@redhat.com>
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Reviewed-by: Ján Tomko <jtomko@redhat.com>
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---
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 src/qemu/qemu_process.c | 30 +++++++++++++++++++++++++++---
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 1 file changed, 27 insertions(+), 3 deletions(-)
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diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
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index d147e524ee..db14d322f5 100644
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--- a/src/qemu/qemu_process.c
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+++ b/src/qemu/qemu_process.c
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@@ -53,6 +53,7 @@
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 #include "qemu_extdevice.h"
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 #include "cpu/cpu.h"
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+#include "cpu/cpu_x86.h"
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 #include "datatypes.h"
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 #include "virlog.h"
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 #include "virerror.h"
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@@ -5226,9 +5227,32 @@ qemuProcessStartValidate(virQEMUDriverPtr driver,
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     if (qemuProcessStartValidateShmem(vm) < 0)
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         return -1;
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-    if (vm->def->cpu &&
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-        virCPUValidateFeatures(vm->def->os.arch, vm->def->cpu) < 0)
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-        return -1;
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+    if (vm->def->cpu) {
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+        if (virCPUValidateFeatures(vm->def->os.arch, vm->def->cpu) < 0)
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+            return -1;
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+
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+        if (ARCH_IS_X86(vm->def->os.arch) &&
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+            !virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_UNAVAILABLE_FEATURES)) {
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+            VIR_AUTOSTRINGLIST features = NULL;
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+            int n;
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+
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+            if ((n = virCPUDefCheckFeatures(vm->def->cpu,
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+                                            virCPUx86FeatureFilterSelectMSR,
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+                                            NULL,
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+                                            &features)) < 0)
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+                return -1;
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+
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+            if (n > 0) {
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+                VIR_AUTOFREE(char *) str = NULL;
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+
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+                str = virStringListJoin((const char **)features, ", ");
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+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
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+                               _("Some features cannot be reliably used "
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+                                 "with this QEMU: %s"), str);
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+                return -1;
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+            }
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+        }
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+    }
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     if (qemuProcessStartValidateDisks(vm, qemuCaps) < 0)
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         return -1;
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-- 
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2.22.0
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