[PATCH 04/11] KVM: SVM: Sync guest's PERF_CNTR_GLOBAL_CTL from h/w only on successful VMRUN

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

Don't (re)read PERF_CNTR_GLOBAL_CTL from hardware on a failed VMRUN, as the
purpose of the read is to synchronize KVM's cache with any writes done by
the guest, and the guest can't possibly have modified the MSR if it never
got a chance to run.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20260904170642.3291466-5-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/svm/svm.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 830ace75e986..f4f488328ea4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4632,6 +4632,10 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 			svm->vmcb->control.erap_ctl &= ~ERAP_CONTROL_CLEAR_RAP;
 
 		vmcb_mark_all_clean(svm->vmcb);
+
+		if (!msr_write_intercepted(svm, MSR_AMD64_PERF_CNTR_GLOBAL_CTL))
+			rdmsrq(MSR_AMD64_PERF_CNTR_GLOBAL_CTL,
+			       vcpu_to_pmu(vcpu)->global_ctrl);
 	}
 
 	/* if exit due to PF check for async PF */
@@ -4641,9 +4645,6 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 
 	kvm_clear_available_registers(vcpu, SVM_REGS_LAZY_LOAD_SET);
 
-	if (!msr_write_intercepted(svm, MSR_AMD64_PERF_CNTR_GLOBAL_CTL))
-		rdmsrq(MSR_AMD64_PERF_CNTR_GLOBAL_CTL, vcpu_to_pmu(vcpu)->global_ctrl);
-
 	trace_kvm_exit(vcpu, KVM_ISA_SVM);
 
 	svm_complete_interrupts(vcpu);
-- 
2.52.0