From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
The kick after setting KVM_REQ_PENDING_TIMER is used to handle the timer
fires on a different pCPU which vCPU is running on, we don't need this
kick when injecting already-expired timer, this kick is expensive since
memory barrier, rcu, preemption disable/enable operations. This patch
reduces the overhead by don't kick vCPU which is injecting already-expired
timer.
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 2 +-
arch/x86/kvm/x86.c | 5 +++--
arch/x86/kvm/x86.h | 2 +-
3 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 248095a..5b5ae66 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1642,7 +1642,7 @@ static void apic_timer_expired(struct kvm_lapic *apic, bool from_timer_fn)
}
atomic_inc(&apic->lapic_timer.pending);
- kvm_set_pending_timer(vcpu);
+ kvm_set_pending_timer(vcpu, from_timer_fn);
}
static void start_sw_tscdeadline(struct kvm_lapic *apic)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 599d732..2a45405 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1778,10 +1778,11 @@ static s64 get_kvmclock_base_ns(void)
}
#endif
-void kvm_set_pending_timer(struct kvm_vcpu *vcpu)
+void kvm_set_pending_timer(struct kvm_vcpu *vcpu, bool should_kick)
{
kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
- kvm_vcpu_kick(vcpu);
+ if (should_kick)
+ kvm_vcpu_kick(vcpu);
}
static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 995ab69..0eaae9c 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -246,7 +246,7 @@ static inline bool kvm_vcpu_latch_init(struct kvm_vcpu *vcpu)
return is_smm(vcpu) || kvm_x86_ops.apic_init_signal_blocked(vcpu);
}
-void kvm_set_pending_timer(struct kvm_vcpu *vcpu);
+void kvm_set_pending_timer(struct kvm_vcpu *vcpu, bool should_kick);
void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr);
--
2.7.4
