KVM: x86: clear bus pointer when destroyed

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: Jiri Slaby <jslaby@suse.cz>

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e7a1166c3eb4b758bfa73a34a2994a16764c746c..659556b28e8321cbffe3a3095920735e9c65b09d 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -587,8 +587,10 @@ static void kvm_destroy_vm(struct kvm *kvm)
        list_del(&kvm->vm_list);
        raw_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);
@@ -3045,6 +3047,14 @@ 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) {