From: Jim Mattson jmattson@google.com
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 jmattson@google.com Reviewed-by: Jacob Xu jacobhxu@google.com Reviewed-by: Peter Shier pshier@google.com Cc: Paolo Bonzini pbonzini@redhat.com Reported-by: Eric Biggers ebiggers@kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com [bwh: Backported to 4.x: adjust indentation] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kvm/cpuid.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -457,7 +457,8 @@ static inline int __do_cpuid_ent(struct 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