On Thu, Aug 11, 2022 at 03:53:50PM +0200, Eugenio Pérez wrote: > Implement suspend operation for vdpa_sim devices, so vhost-vdpa will offer > that backend feature and userspace can effectively suspend the device. > > This is a must before getting virtqueue indexes (base) for live migration, > since the device could modify them after userland gets them. There are > individual ways to perform that action for some devices > (VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no > way to perform it for any vhost device (and, in particular, vhost-vdpa). > > After a successful return of ioctl the device must not process more virtqueue > descriptors. The device can answer to read or writes of config fields as if it > were not suspended. In particular, writing to "queue_enable" with a value of 1 > will not make the device start processing virtqueue buffers. > > In the future, we will provide features similar to > VHOST_USER_GET_INFLIGHT_FD so the device can save pending operations. > > Applied on top of vhost branch. > > Comments are welcome. > > v8: > * v7 but incremental from vhost instead of isolated. Now I'm lost. incremental to what? Does the vhost branch now have the correct bits? > v7: > * Remove ioctl leftover argument and update doc accordingly. > > v6: > * Remove the resume operation, making the ioctl simpler. We can always add > another ioctl for VM_STOP/VM_RESUME operation later. > * s/stop/suspend/ to differentiate more from reset. > * Clarify scope of the suspend operation. > > v5: > * s/not stop/resume/ in doc. > > v4: > * Replace VHOST_STOP to VHOST_VDPA_STOP in vhost ioctl switch case too. > > v3: > * s/VHOST_STOP/VHOST_VDPA_STOP/ > * Add documentation and requirements of the ioctl above its definition. > > v2: > * Replace raw _F_STOP with BIT_ULL(_F_STOP). > * Fix obtaining of stop ioctl arg (it was not obtained but written). > * Add stop to vdpa_sim_blk. > > [1] git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git > > Eugenio Pérez (3): > vdpa: delete unreachable branch on vdpasim_suspend > vdpa: Remove wrong doc of VHOST_VDPA_SUSPEND ioctl > vhost: Remove invalid parameter of VHOST_VDPA_SUSPEND ioctl > > drivers/vdpa/vdpa_sim/vdpa_sim.c | 7 ------- > include/linux/vdpa.h | 2 +- > include/uapi/linux/vhost.h | 17 ++++++----------- > 3 files changed, 7 insertions(+), 19 deletions(-) > > -- > 2.31.1 >
