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>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 1ff1630..c194e49 100644 (file)
--- 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))