diff options
authorJim Mattson <>2019-12-13 16:15:15 -0800
committerGreg Kroah-Hartman <>2020-04-24 07:57:20 +0200
commit5706d13e270a64902dbd0729718aff81f8f3b9d4 (patch)
parente7ed14dae7250ec820ef7883341273c0c84bd83b (diff)
kvm: x86: Host feature SSBD doesn't imply guest feature SPEC_CTRL_SSBD
commit 396d2e878f92ec108e4293f1c77ea3bc90b414ff upstream. The host reports support for the synthetic feature X86_FEATURE_SSBD when any of the three following hardware features are set: CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] CPUID.80000008H:EBX.AMD_SSBD[bit 24] CPUID.80000008H:EBX.VIRT_SSBD[bit 25] Either of the first two hardware features implies the existence of the IA32_SPEC_CTRL MSR, but CPUID.80000008H:EBX.VIRT_SSBD[bit 25] does not. Therefore, CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] should only be set in the guest if CPUID.(EAX=7,ECX=0):EDX.SSBD[bit 31] or CPUID.80000008H:EBX.AMD_SSBD[bit 24] is set on the host. Fixes: 0c54914d0c52a ("KVM: x86: use Intel speculation bugs and features as derived in generic x86 code") Signed-off-by: Jim Mattson <> Reviewed-by: Jacob Xu <> Reviewed-by: Peter Shier <> Cc: Paolo Bonzini <> Reported-by: Eric Biggers <> Signed-off-by: Paolo Bonzini <> [bwh: Backported to 4.x: adjust indentation] Signed-off-by: Ben Hutchings <> Signed-off-by: Sasha Levin <>
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index f876414ca8a3..13bda3fcf42b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -457,7 +457,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
entry->edx |= F(SPEC_CTRL);
if (boot_cpu_has(X86_FEATURE_STIBP))
entry->edx |= F(INTEL_STIBP);
- if (boot_cpu_has(X86_FEATURE_SSBD))
+ if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
+ boot_cpu_has(X86_FEATURE_AMD_SSBD))
entry->edx |= F(SPEC_CTRL_SSBD);
* We emulate ARCH_CAPABILITIES in software even