[PATCH v2 23/66] KVM: x86: Clear output regs for CPUID 0x14 if PT isn't exposed to guest

Sean Christopherson
2020-03-02T23:59:30Z

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>
---
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 1ff16300a468..c194e49622b9 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))
--
2.24.1