lkml.org 
[lkml]   [2011]   [Jan]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH v3 3/3] 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>
---
include/linux/kvm_host.h | 6 ------
virt/kvm/kvm_main.c | 9 +++------
2 files changed, 3 insertions(+), 12 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b99eacd..c8dee22 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -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)) {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 71a4eaf..c9eed53 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -147,11 +147,9 @@ 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 */
@@ -167,7 +165,7 @@ 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;
}
@@ -433,7 +431,6 @@ 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);
--
1.7.3.4

\
 
 \ /
  Last update: 2011-01-12 08:43    [from the cache]
©2003-2011 Jasper Spaans