Re: [Qemu-devel] [PATCH 1.0] virtio-blk: pass full status to the guest

[Michael S. Tsirkin]

On Wed, Nov 02, 2011 at 01:19:40PM +0100, Paolo Bonzini wrote:
> When SCSI passthrough is being used by the guest with virtio-blk, the
> guest is not able to detect disk failures.  This is because the status
> field is expected by the guest driver to include also the msg_status,
> host_status and driver_status fields, but the device is only passing
> down the SCSI status.
> 
> The patch fixes this, and also makes sure that the guest always sees a
> CHECK_CONDITION status when there is valid sense data.

Do the bit offsets happen to be defined in some header?
Also, Signed-off-by is missing?

> ---
>       Sorry for missing the -rc deadline, testing this requires
>       Fibre Channel stuff so I needed someone to do it for me. :)
> 
>  hw/virtio-blk.c |   16 +++++++++++++++-
>  1 files changed, 15 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index 179747a..8beaa20 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -16,6 +16,7 @@
>  #include "trace.h"
>  #include "blockdev.h"
>  #include "virtio-blk.h"
> +#include "scsi-defs.h"
>  #ifdef __linux__
>  # include <scsi/sg.h>
>  #endif
> @@ -231,7 +232,20 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>          status = VIRTIO_BLK_S_OK;
>      }
>  
> -    stl_p(&req->scsi->errors, hdr.status);
> +    /*
> +     * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
> +     * clear the masked_status field [hence status gets cleared too, see
> +     * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
> +     * status has occurred.  However they do set DRIVER_SENSE in 
> driver_status
> +     * field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
> +     */
> +    if (hdr.status == 0 && hdr.sb_len_wr > 0) {
> +        hdr.status = CHECK_CONDITION;
> +    }
> +
> +    stl_p(&req->scsi->errors,
> +          hdr.status | (hdr.msg_status << 8) |
> +          (hdr.host_status << 16) | (hdr.driver_status << 24));
>      stl_p(&req->scsi->residual, hdr.resid);
>      stl_p(&req->scsi->sense_len, hdr.sb_len_wr);
>      stl_p(&req->scsi->data_len, hdr.dxfer_len);
> -- 
> 1.7.6.4