On Tue, Jul 17, 2012 at 01:55:42PM -0500, Anthony Liguori wrote: > On 07/17/2012 10:05 AM, Michael S. Tsirkin wrote: > >On Wed, Jul 11, 2012 at 09:15:00PM +0000, Nicholas A. Bellinger wrote: > >>From: Nicholas Bellinger<nab@xxxxxxxxxxxxxxx> > >> > >>Hi folks, > >> > >>The following is a RFC-v2 series of tcm_vhost target fabric driver code > >>currently in-flight for-3.6 mainline code. > >> > >>After last week's developments along with the help of some new folks, the > >>changelog v1 -> v2 so far looks like: > >> > >>*) Fix drivers/vhost/test.c to use VHOST_NET_FEATURES in patch #1 (Asias He) > >>*) Fix tv_cmd completion -> release SGL memory leak (nab) > >>*) Fix sparse warnings for static variable usage (Fengguang Wu) > >>*) Fix sparse warnings for min() typing + printk format specs (Fengguang Wu) > >>*) Convert to cmwq submission for I/O dispatch (nab + hch) > >> > >>Also following Paolo's request, a patch for hw/virtio-scsi.c that sets > >>scsi_host->max_target=0 that removes the need for virtio-scsi LLD to hardcode > >>VirtIOSCSIConfig->max_id=1 in order to function with tcm_vhost. > >> > >>Note this series has been pushed into target-pending.git/for-next-merge, and > >>should be getting picked up for tomorrow's linux-next build. > >> > >>Please let us know if you have any concerns and/or additional review feedback. > >> > >>Thank you! > > > > > >It still seems not 100% clear whether this driver will have major > >userspace using it. And if not, it would be very hard to support a driver > >when recent userspace does not use it in the end. > > I don't think this is a good reason to exclude something from the > kernel. However, there are good reasons why this doesn't make sense > for something like QEMU--specifically because we have a large number > of features in our block layer that tcm_vhost would bypass. > > But perhaps it makes sense for something like native kvm tool. And > if it did go into the kernel, we would certainly support it in QEMU. > > But I do think the kernel should carefully consider whether it wants > to support an interface like this. This an extremely complicated > ABI with a lot of subtle details around state and compatibility. > > Are you absolutely confident that you can support a userspace > application that expects to get exactly the same response from all > possible commands in 20 kernel versions from now? Virtualization > requires absolutely precise compatibility in terms of bugs and > features. This is probably not something the TCM stack has had to > consider yet. > > >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. > > I think this is a good idea. Even if it goes in, a really clear > policy would be needed wrt the userspace ABI. > > While tcm_vhost is probably more useful than vhost_blk, it's a much > more complex ABI to maintain. > > Regards, > > Anthony Liguori Maybe something like a whitelist of features will help? Might even be a good idea to make it user controllable. > >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. > > > > > >>Nicholas Bellinger (2): > >> vhost: Add vhost_scsi specific defines > >> tcm_vhost: Initial merge for vhost level target fabric driver > >> > >>Stefan Hajnoczi (2): > >> vhost: Separate vhost-net features from vhost features > >> vhost: make vhost work queue visible > >> > >> drivers/vhost/Kconfig | 6 + > >> drivers/vhost/Makefile | 1 + > >> drivers/vhost/net.c | 4 +- > >> drivers/vhost/tcm_vhost.c | 1609 +++++++++++++++++++++++++++++++++++++++++++++ > >> drivers/vhost/tcm_vhost.h | 74 ++ > >> drivers/vhost/test.c | 4 +- > >> drivers/vhost/vhost.c | 5 +- > >> drivers/vhost/vhost.h | 6 +- > >> include/linux/vhost.h | 9 + > >> 9 files changed, 1710 insertions(+), 8 deletions(-) > >> create mode 100644 drivers/vhost/tcm_vhost.c > >> create mode 100644 drivers/vhost/tcm_vhost.h > >> > >>-- > >>1.7.2.5 > > -- 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
