From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43312 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933414AbdC3INB (ORCPT ); Thu, 30 Mar 2017 04:13:01 -0400 Subject: Patch "virtio_balloon: init 1st buffer in stats vq" has been added to the 4.4-stable tree To: lprosek@redhat.com, gregkh@linuxfoundation.org, mst@redhat.com Cc: , From: Date: Thu, 30 Mar 2017 10:12:08 +0200 Message-ID: <149086152856222@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled virtio_balloon: init 1st buffer in stats vq to the 4.4-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: virtio_balloon-init-1st-buffer-in-stats-vq.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From fc8653228c8588a120f6b5dad6983b7b61ff669e Mon Sep 17 00:00:00 2001 From: Ladi Prosek Date: Thu, 23 Mar 2017 08:04:18 +0100 Subject: virtio_balloon: init 1st buffer in stats vq From: Ladi Prosek commit fc8653228c8588a120f6b5dad6983b7b61ff669e upstream. When init_vqs runs, virtio_balloon.stats is either uninitialized or contains stale values. The host updates its state with garbage data because it has no way of knowing that this is just a marker buffer used for signaling. This patch updates the stats before pushing the initial buffer. Alternative fixes: * Push an empty buffer in init_vqs. Not easily done with the current virtio implementation and violates the spec "Driver MUST supply the same subset of statistics in all buffers submitted to the statsq". * Push a buffer with invalid tags in init_vqs. Violates the same spec clause, plus "invalid tag" is not really defined. Note: the spec says: When using the legacy interface, the device SHOULD ignore all values in the first buffer in the statsq supplied by the driver after device initialization. Note: Historically, drivers supplied an uninitialized buffer in the first buffer. Unfortunately QEMU does not seem to implement the recommendation even for the legacy interface. Signed-off-by: Ladi Prosek Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman --- drivers/virtio/virtio_balloon.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -416,6 +416,8 @@ static int init_vqs(struct virtio_balloo * Prime this virtqueue with one buffer so the hypervisor can * use it to signal us later (it can't be broken yet!). */ + update_balloon_stats(vb); + sg_init_one(&sg, vb->stats, sizeof vb->stats); if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL) < 0) Patches currently in stable-queue which might be from lprosek@redhat.com are queue-4.4/virtio_balloon-init-1st-buffer-in-stats-vq.patch queue-4.4/kvm-nvmx-invvpid-handling-improvements.patch