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? > static_call_cond(kvm_x86_pmu_restore_pmu_context)(vcpu); > > /*
