KVM: x86: reinstate vendor-agnostic check on SPEC_CTRL cpuid bits

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Until commit e7c587da12 ("x86/speculation: Use synthetic bits for
IBRS/IBPB/STIBP"), KVM was testing both Intel and AMD CPUID bits before
allowing the guest to write MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD.
Testing only Intel bits on VMX processors, or only AMD bits on SVM
processors, fails if the guests are created with the "opposite" vendor
as the host.

While at it, also tweak the host CPU check to use the vendor-agnostic
feature bit X86_FEATURE_IBPB, since we only care about the availability
of the MSR on the host here and not about specific CPUID bits.

Fixes: e7c587da12 ("x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP")
Cc: stable@vger.kernel.org
Reported-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Paolo Bonzini 2020-12-03 09:40:15 -05:00

parent 2224fc9efb

commit 39485ed95d

3 changed files with 22 additions and 14 deletions

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14

arch/x86/kvm/cpuid.h

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14

arch/x86/kvm/svm/svm.c

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8

arch/x86/kvm/vmx/vmx.c

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