Patch "KVM: x86: clear bus pointer when destroyed" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

KVM: x86: clear bus pointer when destroyed

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-x86-clear-bus-pointer-when-destroyed.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Peter Xu <[email protected]>
Date: Wed, 15 Mar 2017 16:01:17 +0800
Subject: KVM: x86: clear bus pointer when destroyed
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From: Peter Xu <[email protected]>

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.

---
 virt/kvm/kvm_main.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

@@ -720,8 +720,10 @@ static void kvm_destroy_vm(struct kvm *k
 	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);

@@ -3568,6 +3570,14 @@ int kvm_io_bus_unregister_dev(struct kvm
 	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) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/kvm-x86-clear-bus-pointer-when-destroyed.patch