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Date: Sun, 19 Aug 2012 09:44:38 +1000
Message-ID: <CAN05THQ3tZ8qO1YDUswG16JkoM3wf=9UMz8ar0M6dZX_gBr_mw@mail.gmail.com>
From: ronnie sahlberg <ronniesahlberg@gmail.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] ISCSI: Force scsi-generic for MMC with
	blank disks
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org

On Sun, Aug 19, 2012 at 8:20 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Il 19/08/2012 00:02, ronnie sahlberg ha scritto:
>> On Sun, Aug 19, 2012 at 7:58 AM, Paolo Bonzini <pbonzini@redhat.com> 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 <ronniesahlberg@gmail.com>
>>>
>>> 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?
>
> Ah, BTW does using -drive ...,format=raw work, or does it hiccup later
> again on something else?
>

format=raw works !

That then begs the question if would it be possible to force
format=raw always for iscsi devices?

A iscsi device as far as I can see would always just be a raw block
device and there would never be a "header" on such devices
so maybe that would be a solution?


regards
ronnie sahlberg