On Wed, 2012-07-18 at 00:34 +0300, Michael S. Tsirkin wrote: > On Tue, Jul 17, 2012 at 02:17:22PM -0700, Nicholas A. Bellinger wrote: > > On Tue, 2012-07-17 at 18:05 +0300, Michael S. Tsirkin wrote: > > > On Wed, Jul 11, 2012 at 09:15:00PM +0000, Nicholas A. Bellinger wrote: > > > > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx> <SNIP> > > I'm happy to commit to working with QEMU + kvm-tool folks to get to a > > series that can (eventually) see vhost-scsi support merged into upstream > > userspace code. > > > > It took roughly 2 years to get the megasas HBA emulation from Dr. Hannes > > merged, but certainly vhost-scsi has alot less moving pieces and > > hopefully alot less controversial bits than the buffer -> SGL > > conversion.. The key word being here 'hopefully'.. ;) > > > > > I think a good idea for 3.6 would be to make it depend on CONFIG_STAGING. > > > Then we don't commit to an ABI. > > > For this, you can add a separate Kconfig and source it from drivers/staging/Kconfig. > > > Maybe it needs to be in a separate directory drivers/vhost/staging/Kconfig. > > > > > > > So tcm_vhost has been marked as Experimental following virtio-scsi. > > > > Wrt to staging, I'd like to avoid mucking with staging because: > > > > *) The code has been posted for review > > *) The code has been converted to use the latest target-core primitives > > *) The code does not require cleanups between staging -> merge > > *) The code has been stable the last 7 days since RFC-v2 with heavy > > staging is not just for code that needs cleanups. > It's for anything that does not guarantee ABI stability yet. > And I think it's a bit early to guarantee ABI stability - 7 days > is not all that long. > I was talking about the new I/O path has been running for 7 days. > See for example Anthony's comments that raise exactly the ABI > issues. > As mentioned in the response to Anthony, we are using the same generic fabric ABI in drivers/target/target_core_fabric_configfs.c since .38. That part is not going to change, and it has not changed for any of the other 7 target fabric modules we've merged into mainline since then. > > Also, tcm_vhost has been marked as Experimental following virtio-scsi. > > I'd much rather leave it at Experimental until we merge upstream > > userspace support. If userspace support never ends up materializing, > > I'm fine with dropping it all together. > > Once it's in kernel you never know who will use this driver. > Experimental does not mean driver can be dropped, staging does. > Yes, that's the point of being in mainline. People using the code, right..? > > However at this point given that there is a 3x performance gap between > > virtio-scsi-raw + virtio-scsi+tcm_vhost for random mixed small block > > I/O, and we still need the latter to do proper SCSI CDB passthrough for > > non TYPE_DISK devices I'm hoping that we can agree on userspace bits > > once tcm_vhost is merged. > > > > --nab > > I do think upstream kernel would help you nail userspace issues too > but at this point it looks like either staging meterial or 3.6 is too > early. > I think for-3.6 is just the right time for this kernel code. Seriously, The basic ABI fabric layout for /sys/kernel/config/target/vhost/ is going to be the same now for-3.6, the same for-3.7, and the same for .38 code. I'd be happy to move tcm_vhost back to drivers/target/ for now, and we move it to drivers/vhost/ once the userspace bits are worked out..? Would that be a reasonable compromise to move forward..? --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
