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@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
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);
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
