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From 4d0430b1f847d672a39c76e6567bb5e88bc33c78 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Fri, 16 Sep 2016 08:38:18 +0200
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Subject: [PATCH] virtio: recalculate vq->inuse after migration
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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Message-id: <1474015098-11019-2-git-send-email-stefanha@redhat.com>
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Patchwork-id: 72372
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O-Subject: [RHEL-7.3 qemu-kvm PATCH 1/1] virtio: recalculate vq->inuse after migration
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Bugzilla: 1376542
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Markus Armbruster <armbru@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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The vq->inuse field is not migrated. Many devices don't hold
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VirtQueueElements across migration so it doesn't matter that vq->inuse
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starts at 0 on the destination QEMU.
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At least virtio-serial, virtio-blk, and virtio-balloon migrate while
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holding VirtQueueElements. For these devices we need to recalculate
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vq->inuse upon load so the value is correct.
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Cc: qemu-stable@nongnu.org
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
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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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(cherry picked from commit bccdef6b1a204db0f41ffb6e24ce373e4d7890d4)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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Conflicts:
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hw/virtio/virtio.c
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Downstream does not have the vq->used_idx field which was added
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upstream as a performance optimization reducing guest memory accesses.
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Replace vq->used_idx with vring_used_idx(&vdev->vq[i]).
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/virtio/virtio.c | 15 +++++++++++++++
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1 file changed, 15 insertions(+)
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diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
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index e67337b..0df4ed3 100644
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--- a/hw/virtio/virtio.c
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+++ b/hw/virtio/virtio.c
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@@ -932,6 +932,21 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
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vdev->vq[i].last_avail_idx, nheads);
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return -1;
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}
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+
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+ /*
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+ * Some devices migrate VirtQueueElements that have been popped
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+ * from the avail ring but not yet returned to the used ring.
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+ */
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+ vdev->vq[i].inuse = vdev->vq[i].last_avail_idx -
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+ vring_used_idx(&vdev->vq[i]);
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+ if (vdev->vq[i].inuse > vdev->vq[i].vring.num) {
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+ error_report("VQ %d size 0x%x < last_avail_idx 0x%x - "
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+ "used_idx 0x%x",
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+ i, vdev->vq[i].vring.num,
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+ vdev->vq[i].last_avail_idx,
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+ vring_used_idx(&vdev->vq[i]));
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+ return -1;
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+ }
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} else if (vdev->vq[i].last_avail_idx) {
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error_report("VQ %d address 0x0 "
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"inconsistent with Host index 0x%x",
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--
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1.8.3.1
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