On Wed, May 25, 2022 at 4:49 AM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > On Wed, May 25, 2022 at 1:06 AM Eugenio Pérez <eperezma@xxxxxxxxxx> wrote: > > > > Implement stop operation for vdpa_sim devices, so vhost-vdpa will offer > > that backend feature and userspace can effectively stop the device. > > > > This is a must before get 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 the return of ioctl with stop != 0, the device MUST finish any > > pending operations like in flight requests. It must also preserve all > > the necessary state (the virtqueue vring base plus the possible device > > specific states) that is required for restoring in the future. The > > device must not change its configuration after that point. > > I'd suggest documenting this in the code maybe around ops->stop()? > I agree it'd be better to put in the source code, but both vdpa_config_ops and ops->stop don't have a lot of space for docs. Would it work to document at drivers/vdpa/vdpa.c:vhost_vdpa_stop() and redirect config ops like "for more info, see vhost_vdpa_stop"? Thanks! > Thanks > > > > > After the return of ioctl with stop == 0, the device can continue > > processing buffers as long as typical conditions are met (vq is enabled, > > DRIVER_OK status bit is enabled, etc). > > > > In the future, we will provide features similar to VHOST_USER_GET_INFLIGHT_FD > > so the device can save pending operations. > > > > Comments are welcome. > > > > 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. > > > > Eugenio Pérez (4): > > vdpa: Add stop operation > > vhost-vdpa: introduce STOP backend feature bit > > vhost-vdpa: uAPI to stop the device > > vdpa_sim: Implement stop vdpa op > > > > drivers/vdpa/vdpa_sim/vdpa_sim.c | 21 +++++++++++++++++ > > drivers/vdpa/vdpa_sim/vdpa_sim.h | 1 + > > drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 3 +++ > > drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 3 +++ > > drivers/vhost/vdpa.c | 34 +++++++++++++++++++++++++++- > > include/linux/vdpa.h | 6 +++++ > > include/uapi/linux/vhost.h | 3 +++ > > include/uapi/linux/vhost_types.h | 2 ++ > > 8 files changed, 72 insertions(+), 1 deletion(-) > > > > -- > > 2.27.0 > > > > >
