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Commit 3cba4130 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Marcelo Tosatti
Browse files

KVM: make make_all_cpus_request() lockless 



Now, we have 'vcpu->mode' to judge whether need to send ipi to other
cpus, this way is very exact, so checking request bit is needless,
then we can drop the spinlock let it's collateral

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 6b7e2d09

include/linux/kvm_host.h

+0 −6
Original line number Diff line number Diff line
@@ -224,7 +224,6 @@ struct kvm_memslots { 


struct kvm {

	spinlock_t mmu_lock;

	raw_spinlock_t requests_lock;

	struct mutex slots_lock;

	struct mm_struct *mm; /* userspace tied to this vm */

	struct kvm_memslots *memslots;
@@ -731,11 +730,6 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) 
	set_bit(req, &vcpu->requests);

}



static inline bool kvm_make_check_request(int req, struct kvm_vcpu *vcpu)

{

	return test_and_set_bit(req, &vcpu->requests);

}



static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)

{

	if (test_bit(req, &vcpu->requests)) {

virt/kvm/kvm_main.c

+3 −6
Original line number Diff line number Diff line
@@ -165,11 +165,9 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) 


	zalloc_cpumask_var(&cpus, GFP_ATOMIC);



	raw_spin_lock(&kvm->requests_lock);

	me = smp_processor_id();

	me = get_cpu();

	kvm_for_each_vcpu(i, vcpu, kvm) {

		if (kvm_make_check_request(req, vcpu))

			continue;

		kvm_make_request(req, vcpu);

		cpu = vcpu->cpu;



		/* Set ->requests bit before we read ->mode */
@@ -185,7 +183,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) 
		smp_call_function_many(cpus, ack_flush, NULL, 1);

	else

		called = false;

	raw_spin_unlock(&kvm->requests_lock);

	put_cpu();

	free_cpumask_var(cpus);

	return called;

}
@@ -468,7 +466,6 @@ static struct kvm *kvm_create_vm(void) 
	kvm->mm = current->mm;

	atomic_inc(&kvm->mm->mm_count);

	spin_lock_init(&kvm->mmu_lock);

	raw_spin_lock_init(&kvm->requests_lock);

	kvm_eventfd_init(kvm);

	mutex_init(&kvm->lock);

	mutex_init(&kvm->irq_lock);