KVM: Fix unlikely kvm_create vs decache_vcpus_on_cpu race

We add the kvm to the vm_list before initializing the vcpu mutexes,
which can be mutex_trylock()'ed by decache_vcpus_on_cpu().

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index a0a3fddba8150dce9271eeb4af6b2d4b566ab453..46efbe70801c920e8b026061f2981471605e013c 100644 (file)
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -297,9 +297,6 @@ static struct kvm *kvm_create_vm(void)
        kvm_io_bus_init(&kvm->pio_bus);
        spin_lock_init(&kvm->lock);
        INIT_LIST_HEAD(&kvm->active_mmu_pages);
-       spin_lock(&kvm_lock);
-       list_add(&kvm->vm_list, &vm_list);
-       spin_unlock(&kvm_lock);
        kvm_io_bus_init(&kvm->mmio_bus);
        for (i = 0; i < KVM_MAX_VCPUS; ++i) {
                struct kvm_vcpu *vcpu = &kvm->vcpus[i];
@@ -309,6 +306,9 @@ static struct kvm *kvm_create_vm(void)
                vcpu->kvm = kvm;
                vcpu->mmu.root_hpa = INVALID_PAGE;
        }
+       spin_lock(&kvm_lock);
+       list_add(&kvm->vm_list, &vm_list);
+       spin_unlock(&kvm_lock);
        return kvm;
 }