[PATCH 24/26] KVM: x86: Clear output regs for CPUID 0x14 if PT isn't exposed to guest

Sean Christopherson
2020-01-29T23:47:13Z

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 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 eb61a1d83598..d06fb54c9c0d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -651,8 +651,10 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
case 0x14: {
int t, times = entry->eax;

- if (!f_intel_pt)
+ if (!f_intel_pt) {
+ entry->eax = entry->ebx = entry->ecx = entry->edx = 0;
break;
+ }

for (t = 1; t <= times; ++t) {
if (*nent >= maxnent)
--
2.24.1