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Commit d94e1dc9 authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: Get rid of KVM_REQ_KICK 



KVM_REQ_KICK poisons vcpu->requests by having a bit set during normal
operation.  This causes the fast path check for a clear vcpu->requests
to fail all the time, triggering tons of atomic operations.

Fix by replacing KVM_REQ_KICK with a vcpu->guest_mode atomic.

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 54b8486f

arch/x86/kvm/x86.c

+10 −7
Original line number Original line Diff line number Diff line
@@ -4604,13 +4604,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
	if (vcpu->fpu_active)

	if (vcpu->fpu_active)

		kvm_load_guest_fpu(vcpu);

		kvm_load_guest_fpu(vcpu);





	local_irq_disable();

	atomic_set(&vcpu->guest_mode, 1);

	smp_wmb();





	clear_bit(KVM_REQ_KICK, &vcpu->requests);

	local_irq_disable();

	smp_mb__after_clear_bit();





	if (vcpu->requests || need_resched() || signal_pending(current)) {

	if (!atomic_read(&vcpu->guest_mode) || vcpu->requests

		set_bit(KVM_REQ_KICK, &vcpu->requests);

	    || need_resched() || signal_pending(current)) {

		atomic_set(&vcpu->guest_mode, 0);

		smp_wmb();

		local_irq_enable();

		local_irq_enable();

		preempt_enable();

		preempt_enable();

		r = 1;

		r = 1;
@@ -4655,7 +4657,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
	if (hw_breakpoint_active())

	if (hw_breakpoint_active())

		hw_breakpoint_restore();

		hw_breakpoint_restore();





	set_bit(KVM_REQ_KICK, &vcpu->requests);

	atomic_set(&vcpu->guest_mode, 0);

	smp_wmb();

	local_irq_enable();

	local_irq_enable();





	++vcpu->stat.exits;

	++vcpu->stat.exits;
@@ -5580,7 +5583,7 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu) 




	me = get_cpu();

	me = get_cpu();

	if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))

	if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))

		if (!test_and_set_bit(KVM_REQ_KICK, &vcpu->requests))

		if (atomic_xchg(&vcpu->guest_mode, 0))

			smp_send_reschedule(cpu);

			smp_send_reschedule(cpu);

	put_cpu();

	put_cpu();

}

}

include/linux/kvm_host.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -81,6 +81,7 @@ struct kvm_vcpu { 
	int vcpu_id;

	int vcpu_id;

	struct mutex mutex;

	struct mutex mutex;

	int   cpu;

	int   cpu;

	atomic_t guest_mode;

	struct kvm_run *run;

	struct kvm_run *run;

	unsigned long requests;

	unsigned long requests;

	unsigned long guest_debug;

	unsigned long guest_debug;