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From:   Yongji Xie <xieyongji@bytedance.com>
Date:   Wed, 23 Jun 2021 13:50:00 +0800
Message-ID: <CACycT3u8=_D3hCtJR+d5BgeUQMce6S7c_6P3CVfvWfYhCQeXFA@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>,
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On Wed, Jun 23, 2021 at 11:31 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> =E5=9C=A8 2021/6/22 =E4=B8=8B=E5=8D=884:14, Yongji Xie =E5=86=99=E9=81=93=
:
> > On Tue, Jun 22, 2021 at 3:50 PM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> =E5=9C=A8 2021/6/22 =E4=B8=8B=E5=8D=883:22, Yongji Xie =E5=86=99=E9=81=
=93:
> >>>> We need fix a way to propagate the error to the userspace.
> >>>>
> >>>> E.g if we want to stop the deivce, we will delay the status reset un=
til
> >>>> we get respose from the userspace?
> >>>>
> >>> I didn't get how to delay the status reset. And should it be a DoS
> >>> that we want to fix if the userspace doesn't give a response forever?
> >>
> >> You're right. So let's make set_status() can fail first, then propagat=
e
> >> its failure via VHOST_VDPA_SET_STATUS.
> >>
> > OK. So we only need to propagate the failure in the vhost-vdpa case, ri=
ght?
>
>
> I think not, we need to deal with the reset for virtio as well:
>
> E.g in register_virtio_devices(), we have:
>
>          /* We always start by resetting the device, in case a previous
>           * driver messed it up.  This also tests that code path a
> little. */
>        dev->config->reset(dev);
>
> We probably need to make reset can fail and then fail the
> register_virtio_device() as well.
>

OK, looks like virtio_add_status() and virtio_device_ready()[1] should
be also modified if we need to propagate the failure in the
virtio-vdpa case. Or do we only need to care about the reset case?

[1] https://lore.kernel.org/lkml/20210517093428.670-1-xieyongji@bytedance.c=
om/

Thanks,
Yongji