netdev - Re: [PATCH v11 25/40] virtio: allow to unbreak/break virtqueue individually

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Date:   Fri, 1 Jul 2022 02:31:18 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        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>,
        Eric Farman <farman@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...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>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-um@...ts.infradead.org, netdev@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        kangjie.xu@...ux.alibaba.com
Subject: Re: [PATCH v11 25/40] virtio: allow to unbreak/break virtqueue
 individually

On Wed, Jun 29, 2022 at 02:56:41PM +0800, Xuan Zhuo wrote:
> This patch allows the new introduced
> __virtqueue_break()/__virtqueue_unbreak() to break/unbreak the
> virtqueue.
> 
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>

I wonder how this interacts with the hardening patches.
Jason?

> ---
>  drivers/virtio/virtio_ring.c | 24 ++++++++++++++++++++++++
>  include/linux/virtio.h       |  3 +++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 5ec43607cc15..7b02be7fce67 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -2744,6 +2744,30 @@ unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
>  }
>  EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
>  
> +/*
> + * This function should only be called by the core, not directly by the driver.
> + */
> +void __virtqueue_break(struct virtqueue *_vq)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +
> +	/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> +	WRITE_ONCE(vq->broken, true);
> +}
> +EXPORT_SYMBOL_GPL(__virtqueue_break);
> +
> +/*
> + * This function should only be called by the core, not directly by the driver.
> + */
> +void __virtqueue_unbreak(struct virtqueue *_vq)
> +{
> +	struct vring_virtqueue *vq = to_vvq(_vq);
> +
> +	/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> +	WRITE_ONCE(vq->broken, false);
> +}

I don't think these "Pairs" comments have any value.


> +EXPORT_SYMBOL_GPL(__virtqueue_unbreak);
> +
>  bool virtqueue_is_broken(struct virtqueue *_vq)
>  {
>  	struct vring_virtqueue *vq = to_vvq(_vq);
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 1272566adec6..dc474a0d48d1 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -138,6 +138,9 @@ bool is_virtio_device(struct device *dev);
>  void virtio_break_device(struct virtio_device *dev);
>  void __virtio_unbreak_device(struct virtio_device *dev);
>  
> +void __virtqueue_break(struct virtqueue *_vq);
> +void __virtqueue_unbreak(struct virtqueue *_vq);
> +
>  void virtio_config_changed(struct virtio_device *dev);
>  #ifdef CONFIG_PM_SLEEP
>  int virtio_device_freeze(struct virtio_device *dev);
> -- 
> 2.31.0