On 7/10/2024 3:31 PM, Zhang, Xiong Y wrote: > >> On 5/6/2024 11:00 AM, Mingwei Zhang wrote: >>> From: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx> >>> >>> Switch PMI handler at KVM context switch boundary because KVM uses a >>> separate maskable interrupt vector other than the NMI handler for the >>> host PMU to process its own PMIs. So invoke the perf API that allows >>> registration of the PMI handler. >>> >>> Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx> >>> Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx> >>> --- >>> arch/x86/kvm/pmu.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index >>> 2ad71020a2c0..a12012a00c11 100644 >>> --- a/arch/x86/kvm/pmu.c >>> +++ b/arch/x86/kvm/pmu.c >>> @@ -1097,6 +1097,8 @@ void kvm_pmu_save_pmu_context(struct kvm_vcpu >> *vcpu) >>> if (pmc->counter) >>> wrmsrl(pmc->msr_counter, 0); >>> } >>> + >>> + x86_perf_guest_exit(); >>> } >>> >>> void kvm_pmu_restore_pmu_context(struct kvm_vcpu *vcpu) @@ -1107,6 >>> +1109,8 @@ void kvm_pmu_restore_pmu_context(struct kvm_vcpu *vcpu) >>> >>> lockdep_assert_irqs_disabled(); >>> >>> + x86_perf_guest_enter(kvm_lapic_get_reg(vcpu->arch.apic, >>> +APIC_LVTPC)); >>> + >> >> Reading the LVTPC for a vCPU that does not have a struct kvm_lapic allocated >> leads to a NULL pointer dereference. I noticed this while trying to run a >> minimalistic guest like https://github.com/dpw/kvm-hello-world >> >> Does this require a kvm_lapic_enabled() or similar check? >> > > Intel processor has lapci_in_kernel() checking in "[RFC PATCH v3 16/54] KVM: x86/pmu: Plumb through pass-through PMU to vcpu for Intel CPUs". > + pmu->passthrough = vcpu->kvm->arch.enable_passthrough_pmu && > + lapic_in_kernel(vcpu); > > AMD processor seems need this checking also. we could move this checking into common place. > Thanks. Adding that fixes the issue. > >>> static_call_cond(kvm_x86_pmu_restore_pmu_context)(vcpu); >>> >>> /* >
