Re: [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive

[Cong Meng <mc@linux.vnet.ibm.com>]

On Wed 22 Aug 2012 10:13:44 PM CST, Paolo Bonzini wrote:
> Il 22/08/2012 15:13, Stefan Hajnoczi ha scritto:
>> http://lists.gnu.org/archive/html/qemu-devel/2010-12/msg01741.html
>>
>> "This is a real problem in practice. IE. the USB CD-ROM on this POWER7
>> blade limits transfers to 0x1e000 bytes for example and the Linux "sr"
>> driver on the guest is going to try to give me bigger requests than that
>> if I don't start limiting them, which will cause all sort of errors."
>>
>> It cannot be fixed for emulated SCSI HBAs in general but it can for
>> virtio-scsi.
>
> For disks, this should be fixed simply by using scsi-block instead of
> scsi-generic.
>
> CD-ROMs are indeed more complicated because burning CDs cannot be done
> with syscalls. :/
>

So, as the problem exist to CD-ROM, I will continue to get these 
patches move on.

As Paolo pointed out,  the only limit is max_sectors (the total size of 
a scatter-list),
I will drop the other 2 parameters.

Paolo, what's your opinion?

Cong

> Paolo
>