| Message ID | 20090617135347.GC14583@amt.cnet (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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.
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);