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SubjectRe: [PATCH 23/61] KVM: x86: Clear output regs for CPUID 0x14 if PT isn't exposed to guest
Date
Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Clear the output regs for the main CPUID 0x14 leaf (index=0) if Intel PT
> isn't exposed to the guest. Leaf 0x14 enumerates Intel PT capabilities
> and should return zeroes if PT is not supported. Incorrectly reporting
> PT capabilities is essentially a cosmetic error, i.e. doesn't negatively
> affect any known userspace/kernel, as the existence of PT itself is
> correctly enumerated via CPUID 0x7.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/cpuid.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d3c93b94abc3..056faf27b14b 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -663,8 +663,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
> break;
> /* Intel PT */
> case 0x14:
> - if (!f_intel_pt)
> + if (!f_intel_pt) {
> + entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
> break;
> + }
>
> for (i = 1, max_idx = entry->eax; i <= max_idx; ++i) {
> if (!do_host_cpuid(array, function, i))

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly

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