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

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Date:   Thu, 11 Aug 2022 07:35:21 +0200
From:   Eugenio Perez Martin <eperezma@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     kvm list <kvm@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jason Wang <jasowang@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        Dinan Gunawardena <dinang@...inx.com>,
        Martin Porter <martinpo@...inx.com>,
        Wu Zongyong <wuzongyong@...ux.alibaba.com>,
        "Uminski, Piotr" <Piotr.Uminski@...el.com>,
        "Dawar, Gautam" <gautam.dawar@....com>, ecree.xilinx@...il.com,
        Martin Petrus Hubertus Habets <martinh@...inx.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Pablo Cascon Katchadourian <pabloc@...inx.com>,
        habetsm.xilinx@...il.com, Laurent Vivier <lvivier@...hat.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>,
        "Kamde, Tanuj" <tanuj.kamde@....com>,
        Longpeng <longpeng2@...wei.com>, Cindy Lu <lulu@...hat.com>,
        Harpreet Singh Anand <hanand@...inx.com>,
        Parav Pandit <parav@...dia.com>,
        Si-Wei Liu <si-wei.liu@...cle.com>,
        Eli Cohen <elic@...dia.com>,
        Xie Yongji <xieyongji@...edance.com>,
        Zhang Min <zhang.min9@....com.cn>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v7 0/4] Implement vdpasim suspend operation

On Wed, Aug 10, 2022 at 9:20 PM Michael S. Tsirkin <mst@...hat.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
> >
>