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From e3e5226d8ed3907bb818eb8db74175c08c011459 Mon Sep 17 00:00:00 2001
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From: Ladi Prosek <lprosek@redhat.com>
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Date: Wed, 5 Oct 2016 17:22:28 +0200
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Subject: [PATCH 6/8] virtio: zero vq->inuse in virtio_reset()
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RH-Author: Ladi Prosek <lprosek@redhat.com>
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Message-id: <1475666548-9186-7-git-send-email-lprosek@redhat.com>
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Patchwork-id: 72485
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O-Subject: [RHEL-7.4 qemu-kvm v2 PATCH 6/6] virtio: zero vq->inuse in virtio_reset()
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Bugzilla: 1393484
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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From: Stefan Hajnoczi <stefanha@redhat.com>
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vq->inuse must be zeroed upon device reset like most other virtqueue
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fields.
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In theory, virtio_reset() just needs assert(vq->inuse == 0) since
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devices must clean up in-flight requests during reset (requests cannot
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not be leaked!).
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In practice, it is difficult to achieve vq->inuse == 0 across reset
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because balloon, blk, 9p, etc implement various different strategies for
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cleaning up requests. Most devices call g_free(elem) directly without
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telling virtio.c that the VirtQueueElement is cleaned up. Therefore
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vq->inuse is not decremented during reset.
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This patch zeroes vq->inuse and trusts that devices are not leaking
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VirtQueueElements across reset.
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I will send a follow-up series that refactors request life-cycle across
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all devices and converts vq->inuse = 0 into assert(vq->inuse == 0) but
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this more invasive approach is not appropriate for stable trees.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Cc: qemu-stable <qemu-stable@nongnu.org>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Reviewed-by: Ladi Prosek <lprosek@redhat.com>
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(cherry picked from commit 4b7f91ed0270a371e1933efa21ba600b6da23ab9)
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Signed-off-by: Ladi Prosek <lprosek@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/virtio/virtio.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
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index 87a7639..cdb21b1 100644
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--- a/hw/virtio/virtio.c
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+++ b/hw/virtio/virtio.c
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@@ -585,6 +585,7 @@ void virtio_reset(void *opaque)
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vdev->vq[i].signalled_used = 0;
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vdev->vq[i].signalled_used_valid = false;
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vdev->vq[i].notification = true;
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+ vdev->vq[i].inuse = 0;
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}
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}
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--
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1.8.3.1
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