On Thu, Nov 25, 2010 at 2:30 AM, FUJITA Tomonori <fujita.tomon...@lab.ntt.co.jp> wrote: > On Wed, 24 Nov 2010 13:38:59 +0000 > Stefan Hajnoczi <stefa...@gmail.com> 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
