Re: [Qemu-devel] Re: [PATCH 0/5]

[Stefan Hajnoczi]

On Thu, Nov 25, 2010 at 2:30 AM, FUJITA Tomonori
<address@hidden> wrote:
> On Wed, 24 Nov 2010 13:38:59 +0000
> Stefan Hajnoczi <address@hidden> wrote:
>
>> > This series adds rebased support for the hw/scsi-bsg.c backstore for 
>> > scsi-bus
>> > compatible HBA emulation in QEMU-KVM on Linux hosts supporting the BSG 
>> > driver
>> > against current mainline qemu-kvm.git/master code.
>>
>> I don't know the Linux SCSI stack, so some basic questions for you :).
>>
>> With scsi-generic I can send SCSI commands to a device.  How is bsg
>> different?  The bsg code looks cleaner than sg but they both boil down
>> to issuing SCSI requests using the Linux block layer AFAICT.
>>
>> Can you explain what advantages this patch series brings over scsi-generic?
>
> The main reason why we invented bsg is that we need the common
> interface to send non SCSI commands. For example, we already use bsg
> for FC stuff:
>
> http://lwn.net/Articles/326338/
>
> We can use the common interface rather than each HW specific interface.
>
> From the perspective of SCSI, the major advantage of bsg is supporting
> bidi commands. I'm not sure qemu will ever need bidi pass through
> support though.

Thanks for the explanations Christoph and Tomonori.

Stefan