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