[PATCH 2/2] KVM: VMX: Allow toggling bits in MSR_IA32_RTIT_CTL when enable bit is cleared

Sean Christopherson
2024-11-01T18:50:38Z

From: Adrian Hunter <adrian.hunter@intel.com>

Allow toggling other bits in MSR_IA32_RTIT_CTL if the enable bit is being
cleared, the existing logic simply ignores the enable bit. E.g. KVM will
incorrectly reject a write of '0' to stop tracing.

Fixes: bf8c55d8dc09 ("KVM: x86: Implement Intel PT MSRs read/write emulation")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
[sean: rework changelog, drop stable@]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/vmx.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 087504fb1589..9b9d115c4824 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1636,7 +1636,8 @@ static int vmx_rtit_ctl_check(struct kvm_vcpu *vcpu, u64 data)
* result in a #GP unless the same write also clears TraceEn.
*/
if ((vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) &&
- ((vmx->pt_desc.guest.ctl ^ data) & ~RTIT_CTL_TRACEEN))
+ (data & RTIT_CTL_TRACEEN) &&
+ data != vmx->pt_desc.guest.ctl)
return 1;

/*
--
2.47.0.163.g1226f6d8fa-goog