Re: [Qemu-devel] [PATCH 4/4] ISCSI: If the device we open is a SMC device, then force the use of sg. We dont have any medium changer emulation so only passthrough via real sg or scsi-generic via iscsi would work anyway.

[Paolo Bonzini <pbonzini@redhat.com>]

Il 26/05/2012 06:56, Ronnie Sahlberg ha scritto:
> Forcing sg also makes qemu skip trying to read from the device to guess the image format by reading from the device (find_image_format()).
> SMC devices do not implement READ6/10/12/16  so it is noit possible to read from them.
> 
> With this patch I can successfully manage a SMC device wiht iscsi in passthrough mode.
> 
> Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> ---
>  block/iscsi.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/block/iscsi.c b/block/iscsi.c
> index a015a52..9ce38b5 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -1032,6 +1032,15 @@ static int iscsi_open(BlockDriverState *bs, const char *filename, int flags)
>      if (iscsi_url != NULL) {
>          iscsi_destroy_url(iscsi_url);
>      }
> +
> +    /* Medium changer. We dont have any emulation for this so this must
> +       be sg ioctl compatible. We force it to be sg, otherwise qemu will try
> +       to read from the device to guess the image format.
> +     */
> +    if (iscsilun->type == TYPE_MEDIUM_CHANGER) {
> +            bs->sg = 1;
> +    }
> +
>      return 0;
>  
>  failed:

Modified to also do the same for tapes, applied to scsi-next branch for 1.2.

Paolo