Messages in this thread | | | Date | Tue, 24 May 2022 09:09:00 +0200 | From | Stefano Garzarella <> | Subject | Re: [PATCH 1/4] vdpa: Add stop operation |
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On Mon, May 23, 2022 at 09:20:14PM +0200, Eugenio Perez Martin wrote: >On Sat, May 21, 2022 at 12:13 PM Si-Wei Liu <si-wei.liu@oracle.com> wrote: >> >> >> >> On 5/20/2022 10:23 AM, Eugenio Pérez wrote: >> > This operation is optional: It it's not implemented, backend feature bit >> > will not be exposed. >> > >> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com> >> > --- >> > include/linux/vdpa.h | 6 ++++++ >> > 1 file changed, 6 insertions(+) >> > >> > diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h >> > index 15af802d41c4..ddfebc4e1e01 100644 >> > --- a/include/linux/vdpa.h >> > +++ b/include/linux/vdpa.h >> > @@ -215,6 +215,11 @@ struct vdpa_map_file { >> > * @reset: Reset device >> > * @vdev: vdpa device >> > * Returns integer: success (0) or error (< 0) >> > + * @stop: Stop or resume the device (optional, but it must >> > + * be implemented if require device stop) >> > + * @vdev: vdpa device >> > + * @stop: stop (true), not stop (false) >> > + * Returns integer: success (0) or error (< 0) >> Is this uAPI meant to address all use cases described in the full blown >> _F_STOP virtio spec proposal, such as: >> >> --------------%<-------------- >> >> ...... the device MUST finish any in flight >> operations after the driver writes STOP. Depending on the device, it >> can do it >> in many ways as long as the driver can recover its normal operation >> if it >> resumes the device without the need of resetting it: >> >> - Drain and wait for the completion of all pending requests until a >> convenient avail descriptor. Ignore any other posterior descriptor. >> - Return a device-specific failure for these descriptors, so the driver >> can choose to retry or to cancel them. >> - Mark them as done even if they are not, if the kind of device can >> assume to lose them. >> --------------%<-------------- >> > >Right, this is totally underspecified in this series. > >I'll expand on it in the next version, but that text proposed to >virtio-comment was complicated and misleading. I find better to get >the previous version description. Would the next description work? > >``` >After the return of ioctl, 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.
For block devices wait for all in-flight requests could take several time.
Could this be a problem if the caller gets stuck on this ioctl?
If it could be a problem, maybe we should use an eventfd to signal that the device is successfully stopped.
Thanks, Stefano
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