Re: [PATCH v7 0/4] Implement vdpasim suspend operation

Eugenio Perez Martin
2022-08-11T05:36:07Z

On Wed, Aug 10, 2022 at 9:20 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Wed, Aug 10, 2022 at 07:15:08PM +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 [1] branch after removing the old commits.
>
> Except, I can't really do this without invaliding all testing.
> Can't you post an incremental patch?
>

Oops, sorry.

I can send it for doc and internal code. But is it ok to remove an
ioctl arg with incremental patches?

Thanks!

> > Comments are welcome.
> >
> > 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 (4):
> > vdpa: Add suspend operation
> > vhost-vdpa: introduce SUSPEND backend feature bit
> > vhost-vdpa: uAPI to suspend the device
> > vdpa_sim: Implement suspend vdpa op
> >
> > drivers/vdpa/vdpa_sim/vdpa_sim.c | 14 +++++++++++
> > 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 | 35 +++++++++++++++++++++++++++-
> > include/linux/vdpa.h | 4 ++++
> > include/uapi/linux/vhost.h | 9 +++++++
> > include/uapi/linux/vhost_types.h | 2 ++
> > 8 files changed, 70 insertions(+), 1 deletion(-)
> >
> > --
> > 2.31.1
> >
>