linux-kernel - Re: Re: [PATCH v7 11/12] vduse: Introduce VDUSE

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Message-ID: <CACycT3ve7YvKF+F+AnTQoJZMPua+jDvGMs_ox8GQe_=SGdeCMA@mail.gmail.com>
Date:   Thu, 27 May 2021 13:08:32 +0800
From:   Yongji Xie <xieyongji@...edance.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Christian Brauner <christian.brauner@...onical.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, bcrl@...ck.org,
        Jonathan Corbet <corbet@....net>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Dan Carpenter <dan.carpenter@...cle.com>, joro@...tes.org,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev@...r.kernel.org, kvm <kvm@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH v7 11/12] vduse: Introduce VDUSE - vDPA Device in Userspace

On Thu, May 27, 2021 at 1:00 PM Jason Wang <jasowang@...hat.com> wrote:
>
>
> 在 2021/5/27 下午12:57, Yongji Xie 写道:
> > On Thu, May 27, 2021 at 12:13 PM Jason Wang <jasowang@...hat.com> wrote:
> >>
> >> 在 2021/5/17 下午5:55, Xie Yongji 写道:
> >>> +
> >>> +static int vduse_dev_msg_sync(struct vduse_dev *dev,
> >>> +                           struct vduse_dev_msg *msg)
> >>> +{
> >>> +     init_waitqueue_head(&msg->waitq);
> >>> +     spin_lock(&dev->msg_lock);
> >>> +     vduse_enqueue_msg(&dev->send_list, msg);
> >>> +     wake_up(&dev->waitq);
> >>> +     spin_unlock(&dev->msg_lock);
> >>> +     wait_event_killable(msg->waitq, msg->completed);
> >>
> >> What happens if the userspace(malicous) doesn't give a response forever?
> >>
> >> It looks like a DOS. If yes, we need to consider a way to fix that.
> >>
> > How about using wait_event_killable_timeout() instead?
>
>
> Probably, and then we need choose a suitable timeout and more important,
> need to report the failure to virtio.
>

Makes sense to me. But it looks like some
vdpa_config_ops/virtio_config_ops such as set_status() didn't have a
return value.  Now I add a WARN_ON() for the failure. Do you mean we
need to add some change for virtio core to handle the failure?

Thanks,
Yongji