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From d3b9c1891a6d05308dd5ea119d2c32c8f98a25da Mon Sep 17 00:00:00 2001
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From: Eduardo Habkost <ehabkost@redhat.com>
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Date: Tue, 30 Jun 2020 23:40:15 -0400
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Subject: [PATCH 1/4] i386: Mask SVM features if nested SVM is disabled
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RH-Author: Eduardo Habkost <ehabkost@redhat.com>
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Message-id: <20200630234015.166253-2-ehabkost@redhat.com>
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Patchwork-id: 97852
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O-Subject: [RHEL-8.3.0 qemu-kvm PATCH 1/1] i386: Mask SVM features if nested SVM is disabled
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Bugzilla: 1835390
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RH-Acked-by: Igor Mammedov <imammedo@redhat.com>
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RH-Acked-by: Bandan Das <bsd@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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QEMU incorrectly validates FEAT_SVM feature flags against
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GET_SUPPORTED_CPUID even if SVM features are being masked out by
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cpu_x86_cpuid(). This can make QEMU print warnings on most AMD
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CPU models, even when SVM nesting is disabled (which is the
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default).
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This bug was never detected before because of a Linux KVM bug:
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until Linux v5.6, KVM was not filtering out SVM features in
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GET_SUPPORTED_CPUID when nested was disabled. This KVM bug was
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fixed in Linux v5.7-rc1, on Linux commit a50718cc3f43 ("KVM:
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nSVM: Expose SVM features to L1 iff nested is enabled").
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Fix the problem by adding a CPUID_EXT3_SVM dependency to all
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FEAT_SVM feature flags in the feature_dependencies table.
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Reported-by: Yanan Fu <yfu@redhat.com>
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Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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Message-Id: <20200623230116.277409-1-ehabkost@redhat.com>
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[Fix testcase. - Paolo]
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit 730319aef0fcb94f11a4a2d32656437fdde7efdd)
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Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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target/i386/cpu.c | 4 ++++
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tests/test-x86-cpuid-compat.c | 4 ++--
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2 files changed, 6 insertions(+), 2 deletions(-)
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diff --git a/target/i386/cpu.c b/target/i386/cpu.c
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index 7d7b016bb7..a343de0c9d 100644
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--- a/target/i386/cpu.c
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+++ b/target/i386/cpu.c
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@@ -1477,6 +1477,10 @@ static FeatureDep feature_dependencies[] = {
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.from = { FEAT_VMX_SECONDARY_CTLS, VMX_SECONDARY_EXEC_ENABLE_VMFUNC },
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.to = { FEAT_VMX_VMFUNC, ~0ull },
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},
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+ {
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+ .from = { FEAT_8000_0001_ECX, CPUID_EXT3_SVM },
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+ .to = { FEAT_SVM, ~0ull },
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+ },
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};
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typedef struct X86RegisterInfo32 {
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diff --git a/tests/test-x86-cpuid-compat.c b/tests/test-x86-cpuid-compat.c
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index e7c075ed98..983aa0719a 100644
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--- a/tests/test-x86-cpuid-compat.c
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+++ b/tests/test-x86-cpuid-compat.c
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@@ -256,7 +256,7 @@ int main(int argc, char **argv)
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"-cpu 486,+invtsc", "xlevel", 0x80000007);
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/* CPUID[8000_000A].EDX: */
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add_cpuid_test("x86/cpuid/auto-xlevel/486/npt",
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- "-cpu 486,+npt", "xlevel", 0x8000000A);
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+ "-cpu 486,+svm,+npt", "xlevel", 0x8000000A);
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/* CPUID[C000_0001].EDX: */
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add_cpuid_test("x86/cpuid/auto-xlevel2/phenom/xstore",
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"-cpu phenom,+xstore", "xlevel2", 0xC0000001);
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@@ -349,7 +349,7 @@ int main(int argc, char **argv)
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"-machine pc-i440fx-2.4 -cpu SandyBridge,",
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"xlevel", 0x80000008);
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add_cpuid_test("x86/cpuid/xlevel-compat/pc-i440fx-2.4/npt-on",
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- "-machine pc-i440fx-2.4 -cpu SandyBridge,+npt",
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+ "-machine pc-i440fx-2.4 -cpu SandyBridge,+svm,+npt",
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"xlevel", 0x80000008);
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#endif
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--
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2.27.0
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