KVM: x86: clear bus pointer when destroyed

BugLink: http://bugs.launchpad.net/bugs/1681875
commit df630b8c1e851b5e265dc2ca9c87222e342c093b upstream.

When releasing the bus, let's clear the bus pointers to mark it out. If
any further device unregister happens on this bus, we know that we're
done if we found the bus being released already.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 482612b4e496f92527d5191a2a8adfa5962e4de8..e2ec3028692ad7c232cabdf652842867ae34aeb5 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -723,8 +723,10 @@ static void kvm_destroy_vm(struct kvm *kvm)
        list_del(&kvm->vm_list);
        spin_unlock(&kvm_lock);
        kvm_free_irq_routing(kvm);
-       for (i = 0; i < KVM_NR_BUSES; i++)
+       for (i = 0; i < KVM_NR_BUSES; i++) {
                kvm_io_bus_destroy(kvm->buses[i]);
+               kvm->buses[i] = NULL;
+       }
        kvm_coalesced_mmio_free(kvm);
 #if defined(CONFIG_MMU_NOTIFIER) && defined(KVM_ARCH_WANT_MMU_NOTIFIER)
        mmu_notifier_unregister(&kvm->mmu_notifier, kvm->mm);
@@ -3578,6 +3580,14 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
        struct kvm_io_bus *new_bus, *bus;
 
        bus = kvm->buses[bus_idx];
+
+       /*
+        * It's possible the bus being released before hand. If so,
+        * we're done here.
+        */
+       if (!bus)
+               return 0;
+
        r = -ENOENT;
        for (i = 0; i < bus->dev_count; i++)
                if (bus->range[i].dev == dev) {