KVM: x86: Optimize NMI watchdog delivery

As suggested by Avi, this patch introduces a counter of VCPUs that have
LVT0 set to NMI mode. Only if the counter > 0, we push the PIT ticks via
all LAPIC LVT0 lines to enable NMI watchdog support.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 59c3ae1..09e6c56 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -361,6 +361,7 @@ struct kvm_arch{
        struct kvm_ioapic *vioapic;
        struct kvm_pit *vpit;
        struct hlist_head irq_ack_notifier_list;
+       int vapics_in_nmi_mode;
 
        int round_robin_prev_vcpu;
        unsigned int tss_addr;

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index b6fcf5a..e665d1c 100644 (file)
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -620,11 +620,12 @@ static void __inject_pit_timer_intr(struct kvm *kvm)
         * LVT0 to NMI delivery. Other PIC interrupts are just sent to
         * VCPU0, and only if its LVT0 is in EXTINT mode.
         */
-       for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-               vcpu = kvm->vcpus[i];
-               if (vcpu)
-                       kvm_apic_nmi_wd_deliver(vcpu);
-       }
+       if (kvm->arch.vapics_in_nmi_mode > 0)
+               for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+                       vcpu = kvm->vcpus[i];
+                       if (vcpu)
+                               kvm_apic_nmi_wd_deliver(vcpu);
+               }
 }
 
 void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu)

diff --cc arch/x86/kvm/lapic.c
Simple merge