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KVM: x86: Clear output regs for CPUID 0x14 if PT isn't exposed to guest 

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.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-03-02 15:56:26 -08:00 committed by Paolo Bonzini
parent 615a4ae1c7
commit 7392079c4e
1 changed files with 3 additions and 1 deletions
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4
arch/x86/kvm/cpuid.c
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@ -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))