Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210615141331.407-1-xieyongji@bytedance.com> <20210615141331.407-10-xieyongji@bytedance.com>
 <adfb2be9-9ed9-ca37-ac37-4cd00bdff349@redhat.com> <CACycT3tAON+-qZev+9EqyL2XbgH5HDspOqNt3ohQLQ8GqVK=EA@mail.gmail.com>
 <1bba439f-ffc8-c20e-e8a4-ac73e890c592@redhat.com> <CACycT3uzMJS7vw6MVMOgY4rb=SPfT2srV+8DPdwUVeELEiJgbA@mail.gmail.com>
 <0aeb7cb7-58e5-1a95-d830-68edd7e8ec2e@redhat.com> <CACycT3uuooKLNnpPHewGZ=q46Fap2P4XCFirdxxn=FxK+X1ECg@mail.gmail.com>
 <e4cdee72-b6b4-d055-9aac-3beae0e5e3e1@redhat.com> <CACycT3u8=_D3hCtJR+d5BgeUQMce6S7c_6P3CVfvWfYhCQeXFA@mail.gmail.com>
 <d2334f66-907c-2e9c-ea4f-f912008e9be8@redhat.com> <CACycT3uCSLUDVpQHdrmuxSuoBDg-4n22t+N-Jm2GoNNp9JYB2w@mail.gmail.com>
 <48cab125-093b-2299-ff9c-3de8c7c5ed3d@redhat.com>
In-Reply-To: <48cab125-093b-2299-ff9c-3de8c7c5ed3d@redhat.com>
From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Thu, 24 Jun 2021 17:16:39 +0800
Message-ID: <CACycT3tS=10kcUCNGYm=dUZsK+vrHzDvB3FSwAzuJCu3t+QuUQ@mail.gmail.com>
Subject: Re: Re: [PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
To:     Jason Wang <jasowang@redhat.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Parav Pandit <parav@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Christian Brauner <christian.brauner@canonical.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jens Axboe <axboe@kernel.dk>, bcrl@kvack.org,
        Jonathan Corbet <corbet@lwn.net>,
        =?UTF-8?Q?Mika_Penttil=C3=A4?= <mika.penttila@nextfour.com>,
        Dan Carpenter <dan.carpenter@oracle.com>, joro@8bytes.org,
        Greg KH <gregkh@linuxfoundation.org>, songmuchun@bytedance.com,
        virtualization <virtualization@lists.linux-foundation.org>,
        netdev@vger.kernel.org, kvm <kvm@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Thu, Jun 24, 2021 at 4:14 PM Jason Wang <jasowang@redhat.com> wrote:
>
>
> =E5=9C=A8 2021/6/24 =E4=B8=8B=E5=8D=8812:46, Yongji Xie =E5=86=99=E9=81=
=93:
> >> So we need to deal with both FEATURES_OK and reset, but probably not
> >> DRIVER_OK.
> >>
> > OK, I see. Thanks for the explanation. One more question is how about
> > clearing the corresponding status bit in get_status() rather than
> > making set_status() fail. Since the spec recommends this way for
> > validation which is done in virtio_dev_remove() and
> > virtio_finalize_features().
> >
> > Thanks,
> > Yongji
> >
>
> I think you can. Or it would be even better that we just don't set the
> bit during set_status().
>

Yes, that's what I mean.

> I just realize that in vdpa_reset() we had:
>
> static inline void vdpa_reset(struct vdpa_device *vdev)
> {
>          const struct vdpa_config_ops *ops =3D vdev->config;
>
>          vdev->features_valid =3D false;
>          ops->set_status(vdev, 0);
> }
>
> We probably need to add the synchronization here. E.g re-read with a
> timeout.
>

Looks like the timeout is already in set_status(). Do we really need a
duplicated one here? And how to handle failure? Adding a return value
to virtio_config_ops->reset() and passing the error to the upper
layer?

Thanks,
Yongji