[3.16.y-ckt stable] Patch "kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt19.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From bc0941e3d57dbe9cc031179399dac3078de71bd4 Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang at redhat.com>
Date: Tue, 15 Sep 2015 14:41:54 +0800
Subject: kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd

commit 8453fecbecae26edb3f278627376caab05d9a88d upstream.

We only want zero length mmio eventfd to be registered on
KVM_FAST_MMIO_BUS. So check this explicitly when arg->len is zero to
make sure this.

Cc: Gleb Natapov <gleb at kernel.org>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck at de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 virt/kvm/eventfd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 20c3af7692c5..47e48e2c7d1a 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -778,7 +778,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 	/* When length is ignored, MMIO is also put on a separate bus, for
 	 * faster lookups.
 	 */
-	if (!args->len && !(args->flags & KVM_IOEVENTFD_FLAG_PIO)) {
+	if (!args->len && bus_idx == KVM_MMIO_BUS) {
 		ret = kvm_io_bus_register_dev(kvm, KVM_FAST_MMIO_BUS,
 					      p->addr, 0, &p->dev);
 		if (ret < 0)
@@ -833,7 +833,7 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
 			continue;

 		kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
-		if (!p->length) {
+		if (!p->length && p->bus_idx == KVM_MMIO_BUS) {
 			kvm_io_bus_unregister_dev(kvm, KVM_FAST_MMIO_BUS,
 						  &p->dev);
 		}