Re: [Qemu-devel] [PATCH 2/2] ISCSI: Force scsi-generic for MMC with blank disks

[ronnie sahlberg]

On Sun, Aug 19, 2012 at 7:58 AM, Paolo Bonzini <address@hidden> wrote:
> Il 17/08/2012 04:36, Ronnie Sahlberg ha scritto:
>> There is no bdrv_* API for the commands for burning a blank MMC disk
>> so when iSCSI LUNs are specified and the LUN is a MMC device with
>> 0 available blocks. This is a blank disk so force scsi generic.
>>
>> This allows the guest to talk directly to the target to burn data on
>> the disk.
>>
>> Signed-off-by: Ronnie Sahlberg <address@hidden>
>
> What happens without the patch?  It's ok that scsi-{hd,cd} does not
> work, but do scsi-{block,generic} work without the patch?
>

Neither of them work, basically because in
block.c:find_image_format()

if bs->sg is not set in

 if (bs->sg || !bdrv_is_inserted(bs)) {

then we continue to

  ret = bdrv_pread(bs, 0, buf, sizeof(buf));

which fails with an error.
So this patch is basically to prevent find_image_format() from trying
to read from a blank disk.

Maybe there is a better way to do this?



regards
ronnie sahlberg