Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220526124338.36247-1-eperezma@redhat.com> <PH0PR12MB54819C6C6DAF6572AEADC1AEDCD99@PH0PR12MB5481.namprd12.prod.outlook.com>
 <20220527065442-mutt-send-email-mst@kernel.org>
In-Reply-To: <20220527065442-mutt-send-email-mst@kernel.org>
From:   Jason Wang <jasowang@redhat.com>
Date:   Mon, 30 May 2022 11:39:21 +0800
Message-ID: <CACGkMEubfv_OJOsJ_ROgei41Qx4mPO0Xz8rMVnO8aPFiEqr8rA@mail.gmail.com>
Subject: Re: [PATCH v4 0/4] Implement vdpasim stop operation
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Parav Pandit <parav@nvidia.com>,
        =?UTF-8?Q?Eugenio_P=C3=A9rez?= <eperezma@redhat.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "martinh@xilinx.com" <martinh@xilinx.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "martinpo@xilinx.com" <martinpo@xilinx.com>,
        "lvivier@redhat.com" <lvivier@redhat.com>,
        "pabloc@xilinx.com" <pabloc@xilinx.com>,
        Eli Cohen <elic@nvidia.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Xie Yongji <xieyongji@bytedance.com>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Zhang Min <zhang.min9@zte.com.cn>,
        Wu Zongyong <wuzongyong@linux.alibaba.com>,
        "lulu@redhat.com" <lulu@redhat.com>,
        Zhu Lingshan <lingshan.zhu@intel.com>,
        "Piotr.Uminski@intel.com" <Piotr.Uminski@intel.com>,
        Si-Wei Liu <si-wei.liu@oracle.com>,
        "ecree.xilinx@gmail.com" <ecree.xilinx@gmail.com>,
        "gautam.dawar@amd.com" <gautam.dawar@amd.com>,
        "habetsm.xilinx@gmail.com" <habetsm.xilinx@gmail.com>,
        "tanuj.kamde@amd.com" <tanuj.kamde@amd.com>,
        "hanand@xilinx.com" <hanand@xilinx.com>,
        "dinang@xilinx.com" <dinang@xilinx.com>,
        Longpeng <longpeng2@huawei.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, May 27, 2022 at 6:56 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, May 26, 2022 at 12:54:32PM +0000, Parav Pandit wrote:
> >
> >
> > > From: Eugenio P=C3=A9rez <eperezma@redhat.com>
> > > Sent: Thursday, May 26, 2022 8:44 AM
> >
> > > Implement stop operation for vdpa_sim devices, so vhost-vdpa will off=
er
> > >
> > > 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 ar=
e
> > >
> > > 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-vdp=
a).
> > >
> > >
> > >
> > > After the return of ioctl with stop !=3D 0, the device MUST finish an=
y
> > >
> > > pending operations like in flight requests. It must also preserve all
> > >
> > > the necessary state (the virtqueue vring base plus the possible devic=
e
> > >
> > > specific states) that is required for restoring in the future. The
> > >
> > > device must not change its configuration after that point.
> > >
> > >
> > >
> > > After the return of ioctl with stop =3D=3D 0, the device can continue
> > >
> > > processing buffers as long as typical conditions are met (vq is enabl=
ed,
> > >
> > > DRIVER_OK status bit is enabled, etc).
> >
> > Just to be clear, we are adding vdpa level new ioctl() that doesn=E2=80=
=99t map to any mechanism in the virtio spec.
> >
> > Why can't we use this ioctl() to indicate driver to start/stop the devi=
ce instead of driving it through the driver_ok?
> > This is in the context of other discussion we had in the LM series.
>
> If there's something in the spec that does this then let's use that.

Actually, we try to propose a independent feature here:

https://lists.oasis-open.org/archives/virtio-dev/202111/msg00020.html

Does it make sense to you?

Thanks

> Unfortunately the LM series seems to be stuck on moving
> bits around with the admin virtqueue ...
>
> --
> MST
>