In-Reply-To: The following patches were made over Michael's vhost branch here: https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/log/?h=vhost They fix a couple issues with vhost-scsi when we hit the 256 cmd limit that result in the guest getting IO errors, add LUN reset support so devices are not offlined during transient errors, allow us to manage vhost scsi IO with cgroups, and imrpove IOPs up to 2X. The following patches are a follow up to this post: https://patchwork.kernel.org/project/target-devel/cover/1600712588-9514-1-git-send-email-michael.christie@xxxxxxxxxx/ which originally was fixing how vhost-scsi handled cmds so we would not get IO errors when sending more than 256 cmds. In that patchset I needed to detect if a vq was in use and for this patch: https://patchwork.kernel.org/project/target-devel/patch/1600712588-9514-3-git-send-email-michael.christie@xxxxxxxxxx/ It was suggested to add support for VHOST_RING_ENABLE. While doing that though I hit a couple problems: 1. The patches moved how vhost-scsi allocated cmds from per lio session to per vhost vq. To support both VHOST_RING_ENABLE and where userspace didn't support it, I would have to keep around the old per session/device cmd allocator/completion and then also maintain the new code. Or, I would still have to use this patch patchwork.kernel.org/cover/11790763/ for the compat case so there adding the new ioctl would not help much. 2. For vhost-scsi I also wanted to prevent where we allocate iovecs for 128 vqs even though we normally use a couple. To do this, I needed something similar to #1, but the problem is that the VHOST_RING_ENABLE call would come too late. To try and balance #1 and #2, these patches just allow vhost-scsi to setup a vq when userspace starts to config it. This allows the driver to only fully setup (we still waste some memory to support older setups but do not have to preallocate everything like before) what is used plus I do not need to maintain 2 code paths. V3: - fix compile errors - fix possible crash where cmd could be freed while adding it to completion list - fix issue where we added the worker thread to the blk cgroup but the blk IO was submitted by a driver workqueue. V2: - fix use before set cpu var errors - drop vhost_vq_is_setup - include patches to do a worker thread per scsi IO vq
