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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: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Xiao Guangrong 2011-01-12 15:41:22 +08:00 committed by Marcelo Tosatti
parent 6b7e2d0991
commit 3cba41307a
2 changed files with 3 additions and 12 deletions
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6
include/linux/kvm_host.h
View File

@ -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)) {

9
virt/kvm/kvm_main.c
View File

@ -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);