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Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Yongwei Ma , Xiong Zhang , Dapeng Mi , Jim Mattson , Sandipan Das , Zide Chen , Eranian Stephane , Shukla Manali , Nikunj Dadhania Content-Type: text/plain; charset="us-ascii" On Mon, Mar 24, 2025, Mingwei Zhang wrote: > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > index 385e3a5fc304..18cd418fe106 100644 > --- a/arch/x86/kernel/irq.c > +++ b/arch/x86/kernel/irq.c > @@ -312,16 +312,22 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_x86_platform_ipi) > static void dummy_handler(void) {} > static void (*kvm_posted_intr_wakeup_handler)(void) = dummy_handler; > > -void kvm_set_posted_intr_wakeup_handler(void (*handler)(void)) > +void x86_set_kvm_irq_handler(u8 vector, void (*handler)(void)) > { > - if (handler) > + if (!handler) > + handler = dummy_handler; > + > + if (vector == POSTED_INTR_WAKEUP_VECTOR && > + (handler == dummy_handler || > + kvm_posted_intr_wakeup_handler == dummy_handler)) > kvm_posted_intr_wakeup_handler = handler; > - else { > - kvm_posted_intr_wakeup_handler = dummy_handler; > + else > + WARN_ON_ONCE(1); > + > + if (handler == dummy_handler) Eww. Aside from the fact that the dummy_handler implementation is pointless overhead, I don't think KVM should own the IRQ vector. Given that perf owns the LVTPC, i.e. responsible for switching between NMI and the medited PMI IRQ, I think perf should also own the vector. KVM can then use the existing perf guest callbacks to wire up its PMI handler. And with that, this patch can be dropped.