* KVM: protect concurrent make_all_cpus_request
@ 2009-06-17 13:53 Marcelo Tosatti
2009-06-17 16:52 ` Andrea Arcangeli
2009-06-18 8:45 ` Avi Kivity
0 siblings, 2 replies; 3+ messages in thread
From: Marcelo Tosatti @ 2009-06-17 13:53 UTC (permalink / raw)
To: kvm, Avi Kivity; +Cc: Andrea Arcangeli
make_all_cpus_request contains a race condition which can
trigger false request completed status, as follows:
CPU0 CPU1
if (test_and_set_bit(req,&vcpu->requests))
.... if (test_and_set_bit(req,&vcpu->requests))
.. return
proceed to smp_call_function_many(wait=1)
Use a spinlock to serialize concurrent CPUs.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1b48092..2451f48 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -124,6 +124,7 @@ struct kvm_kernel_irq_routing_entry {
struct kvm {
spinlock_t mmu_lock;
+ spinlock_t requests_lock;
struct rw_semaphore slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
int nmemslots;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8939ffa..6847bb7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -739,6 +739,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
cpumask_clear(cpus);
me = get_cpu();
+ spin_lock(&kvm->requests_lock);
kvm_for_each_vcpu(i, vcpu, kvm) {
if (test_and_set_bit(req, &vcpu->requests))
continue;
@@ -752,6 +753,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
smp_call_function_many(cpus, ack_flush, NULL, 1);
else
called = false;
+ spin_unlock(&kvm->requests_lock);
put_cpu();
free_cpumask_var(cpus);
return called;
@@ -972,6 +974,7 @@ static struct kvm *kvm_create_vm(void)
kvm->mm = current->mm;
atomic_inc(&kvm->mm->mm_count);
spin_lock_init(&kvm->mmu_lock);
+ spin_lock_init(&kvm->requests_lock);
kvm_io_bus_init(&kvm->pio_bus);
kvm_irqfd_init(kvm);
mutex_init(&kvm->lock);
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: KVM: protect concurrent make_all_cpus_request
2009-06-17 13:53 KVM: protect concurrent make_all_cpus_request Marcelo Tosatti
@ 2009-06-17 16:52 ` Andrea Arcangeli
2009-06-18 8:45 ` Avi Kivity
1 sibling, 0 replies; 3+ messages in thread
From: Andrea Arcangeli @ 2009-06-17 16:52 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: kvm, Avi Kivity
On Wed, Jun 17, 2009 at 10:53:47AM -0300, Marcelo Tosatti wrote:
>
>
> make_all_cpus_request contains a race condition which can
> trigger false request completed status, as follows:
>
> CPU0 CPU1
>
> if (test_and_set_bit(req,&vcpu->requests))
> .... if (test_and_set_bit(req,&vcpu->requests))
> .. return
> proceed to smp_call_function_many(wait=1)
>
> Use a spinlock to serialize concurrent CPUs.
Agreed, this is the safest...
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: KVM: protect concurrent make_all_cpus_request
2009-06-17 13:53 KVM: protect concurrent make_all_cpus_request Marcelo Tosatti
2009-06-17 16:52 ` Andrea Arcangeli
@ 2009-06-18 8:45 ` Avi Kivity
1 sibling, 0 replies; 3+ messages in thread
From: Avi Kivity @ 2009-06-18 8:45 UTC (permalink / raw)
To: Marcelo Tosatti; +Cc: kvm, Andrea Arcangeli
On 06/17/2009 04:53 PM, Marcelo Tosatti wrote:
> make_all_cpus_request contains a race condition which can
> trigger false request completed status, as follows:
>
> CPU0 CPU1
>
> if (test_and_set_bit(req,&vcpu->requests))
> .... if (test_and_set_bit(req,&vcpu->requests))
> .. return
> proceed to smp_call_function_many(wait=1)
>
> Use a spinlock to serialize concurrent CPUs.
>
>
Applied, thanks.
--
error compiling committee.c: too many arguments to function
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-06-18 8:45 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-06-17 13:53 KVM: protect concurrent make_all_cpus_request Marcelo Tosatti
2009-06-17 16:52 ` Andrea Arcangeli
2009-06-18 8:45 ` Avi Kivity
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.