On Mon, May 06, 2024, Yi Wang wrote: > From: Yi Wang <foxywang@xxxxxxxxxxx> > > We found that it may cost more than 20 milliseconds very accidentally > to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms > already. > > The reason is that when vmm(qemu/CloudHypervisor) invokes > KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and > might_sleep and kworker of srcu may cost some delay during this period. > > As we have set up empty irq routing when creating vm, so this is no > need now. > > Signed-off-by: Yi Wang <foxywang@xxxxxxxxxxx> > --- > arch/x86/kvm/irq.h | 1 - > arch/x86/kvm/irq_comm.c | 5 ----- > arch/x86/kvm/x86.c | 3 --- > 3 files changed, 9 deletions(-) > > diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h > index c2d7cfe82d00..76d46b2f41dd 100644 > --- a/arch/x86/kvm/irq.h > +++ b/arch/x86/kvm/irq.h > @@ -106,7 +106,6 @@ void __kvm_migrate_timers(struct kvm_vcpu *vcpu); > int apic_has_pending_timer(struct kvm_vcpu *vcpu); > > int kvm_setup_default_irq_routing(struct kvm *kvm); > -int kvm_setup_empty_irq_routing(struct kvm *kvm); > int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > struct kvm_lapic_irq *irq, > struct dest_map *dest_map); > diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c > index 68f3f6c26046..6ee7ca39466e 100644 > --- a/arch/x86/kvm/irq_comm.c > +++ b/arch/x86/kvm/irq_comm.c > @@ -397,11 +397,6 @@ int kvm_setup_default_irq_routing(struct kvm *kvm) > > static const struct kvm_irq_routing_entry empty_routing[] = {}; empty_routing is unused after this patch and can+should be removed, e.g. arch/x86/kvm/irq_comm.c:398:43: error: ‘empty_routing’ defined but not used [-Werror=unused-const-variable=] 398 | static const struct kvm_irq_routing_entry empty_routing[] = {}; I'll fix this up when applying, too.