netdev - Re: [PATCH v9 02/32] virtio: struct virtio_config_ops add callbacks for queue

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Date:   Tue, 12 Apr 2022 10:49:20 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        virtualization <virtualization@...ts.linux-foundation.org>
Cc:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        Vadim Pasternak <vadimp@...dia.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Cornelia Huck <cohuck@...hat.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev <netdev@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm <kvm@...r.kernel.org>,
        "open list:XDP (eXpress Data Path)" <bpf@...r.kernel.org>
Subject: Re: [PATCH v9 02/32] virtio: struct virtio_config_ops add callbacks
 for queue_reset

On Tue, Apr 12, 2022 at 10:47 AM Jason Wang <jasowang@...hat.com> wrote:
>
>
> 在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> > Performing reset on a queue is divided into four steps:
> >
> >   1. transport: notify the device to reset the queue
> >   2. vring:     recycle the buffer submitted
> >   3. vring:     reset/resize the vring (may re-alloc)
> >   4. transport: mmap vring to device, and enable the queue
>
>
> Nit: it looks to me we'd better say it's an example (since step 3 or
> even 2 is not a must).
>
>
> >
> > In order to support queue reset, add two callbacks(reset_vq,
> > enable_reset_vq) in struct virtio_config_ops to implement steps 1 and 4.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >   include/linux/virtio_config.h | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> >
> > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> > index 4d107ad31149..d4adcd0e1c57 100644
> > --- a/include/linux/virtio_config.h
> > +++ b/include/linux/virtio_config.h
> > @@ -74,6 +74,16 @@ struct virtio_shm_region {
> >    * @set_vq_affinity: set the affinity for a virtqueue (optional).
> >    * @get_vq_affinity: get the affinity for a virtqueue (optional).
> >    * @get_shm_region: get a shared memory region based on the index.
> > + * @reset_vq: reset a queue individually (optional).
> > + *   vq: the virtqueue
> > + *   Returns 0 on success or error status
> > + *   reset_vq will guarantee that the callbacks are disabled and synchronized.
> > + *   Except for the callback, the caller should guarantee that the vring is
>
>
> I wonder what's the implications for virtio hardening[1]. In that

For [1] I meant
https://lore.kernel.org/lkml/20220406083538.16274-1-jasowang@redhat.com/

Thanks


> series, we agree to have a synchronize_vqs() config ops to make sure
> callbacks are synchronized.
>
> It uses a global flag and a device wise synchronization mechanism. It
> looks to me we need to switch to
>
> 1) per virtqueue flag
> 2) per virtqueue synchronization
>
> Thanks
>
>
> > + *   not accessed by any functions of virtqueue.
> > + * @enable_reset_vq: enable a reset queue
> > + *   vq: the virtqueue
> > + *   Returns 0 on success or error status
> > + *   If reset_vq is set, then enable_reset_vq must also be set.
> >    */
> >   typedef void vq_callback_t(struct virtqueue *);
> >   struct virtio_config_ops {
> > @@ -100,6 +110,8 @@ struct virtio_config_ops {
> >                       int index);
> >       bool (*get_shm_region)(struct virtio_device *vdev,
> >                              struct virtio_shm_region *region, u8 id);
> > +     int (*reset_vq)(struct virtqueue *vq);
> > +     int (*enable_reset_vq)(struct virtqueue *vq);
> >   };
> >
> >   /* If driver didn't advertise the feature, it will never appear. */