virtio: reset device on bad guest index in virtio_load()
If we find a queue with an inconsistent guest index value, explicitly mark the device as needing a reset - and broken - via virtio_error(). There's at least one driver implementation - the virtio-win NetKVM driver - that is able to handle a VIRTIO_CONFIG_S_NEEDS_RESET notification and successfully restore the device to a working state. Other implementations do not correctly handle this, but as the VQ is not in a functional state anyway, this is still worth doing. Signed-off-by: John Levon <john.levon@nutanix.com> Message-Id: <20201120185103.GA442386@sent> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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@ -3161,12 +3161,15 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
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nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
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/* Check it isn't doing strange things with descriptor numbers. */
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if (nheads > vdev->vq[i].vring.num) {
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qemu_log_mask(LOG_GUEST_ERROR,
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"VQ %d size 0x%x Guest index 0x%x "
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"inconsistent with Host index 0x%x: delta 0x%x",
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i, vdev->vq[i].vring.num,
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vring_avail_idx(&vdev->vq[i]),
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vdev->vq[i].last_avail_idx, nheads);
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virtio_error(vdev, "VQ %d size 0x%x Guest index 0x%x "
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"inconsistent with Host index 0x%x: delta 0x%x",
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i, vdev->vq[i].vring.num,
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vring_avail_idx(&vdev->vq[i]),
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vdev->vq[i].last_avail_idx, nheads);
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vdev->vq[i].used_idx = 0;
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vdev->vq[i].shadow_avail_idx = 0;
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vdev->vq[i].inuse = 0;
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continue;
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}
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vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]);
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vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);
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