From 55783a5521a3b1f93ee6a072e414a27c6cfa15f0 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 7 Nov 2014 14:00:02 +0100 Subject: [PATCH] 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 --- hw/scsi/virtio-scsi.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index fdcacfd..ef48550 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -118,6 +118,7 @@ static size_t qemu_sgl_concat(VirtIOSCSIReq *req, struct iovec *iov, static int virtio_scsi_parse_req(VirtIOSCSIReq *req, unsigned req_size, unsigned resp_size) { + VirtIODevice *vdev = (VirtIODevice *) req->dev; size_t in_size, out_size; if (iov_to_buf(req->elem.out_sg, req->elem.out_num, 0, @@ -130,8 +131,24 @@ static int virtio_scsi_parse_req(VirtIOSCSIReq *req, resp_size) < resp_size) { return -EINVAL; } + req->resp_size = resp_size; + /* Old BIOSes left some padding by mistake after the req_size/resp_size. + * As a workaround, always consider the first buffer as the virtio-scsi + * request/response, making the payload start at the second element + * of the iovec. + * + * The actual length of the response header, stored in req->resp_size, + * does not change. + * + * TODO: always disable this workaround for virtio 1.0 devices. + */ + if ((vdev->guest_features & VIRTIO_F_ANY_LAYOUT) == 0) { + req_size = req->elem.out_sg[0].iov_len; + resp_size = req->elem.in_sg[0].iov_len; + } + out_size = qemu_sgl_concat(req, req->elem.out_sg, &req->elem.out_addr[0], req->elem.out_num, req_size); -- 2.7.4