virtio-scsi: work around bug in old BIOSes
Old BIOSes left some padding by mistake after the req_size/resp_size. New QEMU does not like it, thinking it is a bidirectional command. As a workaround, we can check if the ANY_LAYOUT bit is set; if not, we always consider the first buffer as the virtio-scsi request/response, because, back when QEMU did not support ANY_LAYOUT, it expected the payload to start at the second element of the iovec. This can show up during migration. Cc: qemu-stable@nongnu.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -118,6 +118,7 @@ static size_t qemu_sgl_concat(VirtIOSCSIReq *req, struct iovec *iov,
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static int virtio_scsi_parse_req(VirtIOSCSIReq *req,
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static int virtio_scsi_parse_req(VirtIOSCSIReq *req,
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unsigned req_size, unsigned resp_size)
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unsigned req_size, unsigned resp_size)
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{
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{
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VirtIODevice *vdev = (VirtIODevice *) req->dev;
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size_t in_size, out_size;
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size_t in_size, out_size;
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if (iov_to_buf(req->elem.out_sg, req->elem.out_num, 0,
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if (iov_to_buf(req->elem.out_sg, req->elem.out_num, 0,
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@ -130,8 +131,24 @@ static int virtio_scsi_parse_req(VirtIOSCSIReq *req,
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resp_size) < resp_size) {
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resp_size) < resp_size) {
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return -EINVAL;
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return -EINVAL;
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}
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}
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req->resp_size = resp_size;
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req->resp_size = resp_size;
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/* Old BIOSes left some padding by mistake after the req_size/resp_size.
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* As a workaround, always consider the first buffer as the virtio-scsi
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* request/response, making the payload start at the second element
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* of the iovec.
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*
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* The actual length of the response header, stored in req->resp_size,
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* does not change.
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*
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* TODO: always disable this workaround for virtio 1.0 devices.
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*/
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if ((vdev->guest_features & VIRTIO_F_ANY_LAYOUT) == 0) {
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req_size = req->elem.out_sg[0].iov_len;
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resp_size = req->elem.in_sg[0].iov_len;
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}
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out_size = qemu_sgl_concat(req, req->elem.out_sg,
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out_size = qemu_sgl_concat(req, req->elem.out_sg,
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&req->elem.out_addr[0], req->elem.out_num,
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&req->elem.out_addr[0], req->elem.out_num,
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req_size);
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req_size);
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