Please apply the attached backport of commit 396d2e878f92ec108e4293f1c77ea3bc90b414ff to the 4.4, 4.9, 4.14, and 4.19 stable branches. Ben. -- Ben Hutchings I say we take off; nuke the site from orbit. It's the only way to be sure.
From: Jim Mattson <jmattson@xxxxxxxxxx>
Date: Fri, 13 Dec 2019 16:15:15 -0800
Subject: 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 <jmattson@xxxxxxxxxx>
Reviewed-by: Jacob Xu <jacobhxu@xxxxxxxxxx>
Reviewed-by: Peter Shier <pshier@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reported-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[bwh: Backported to 4.x: adjust indentation]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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
@@ -400,7 +400,8 @@ 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
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