netdev - Re: [PATCH v7 08/26] virtio_ring: extract the logic of freeing vring

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Message-ID: <1646817741.6086373-5-xuanzhuo@linux.alibaba.com>
Date:   Wed, 9 Mar 2022 17:22:21 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Jason Wang <jasowang@...hat.com>
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, platform-driver-x86@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, bpf@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH v7 08/26] virtio_ring: extract the logic of freeing vring

On Wed, 9 Mar 2022 15:51:13 +0800, Jason Wang <jasowang@...hat.com> wrote:
>
> 在 2022/3/8 下午8:35, Xuan Zhuo 写道:
> > Introduce vring_free() to free the vring of vq.
> >
> > Prevent double free by setting vq->reset.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >   drivers/virtio/virtio_ring.c | 25 ++++++++++++++++++++-----
> >   include/linux/virtio.h       |  8 ++++++++
> >   2 files changed, 28 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index b5a9bf4f45b3..e0422c04c903 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -2442,14 +2442,10 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
> >   }
> >   EXPORT_SYMBOL_GPL(vring_new_virtqueue);
> >
> > -void vring_del_virtqueue(struct virtqueue *_vq)
> > +static void __vring_free(struct virtqueue *_vq)
> >   {
> >   	struct vring_virtqueue *vq = to_vvq(_vq);
> >
> > -	spin_lock(&vq->vq.vdev->vqs_list_lock);
> > -	list_del(&_vq->list);
> > -	spin_unlock(&vq->vq.vdev->vqs_list_lock);
> > -
> >   	if (vq->we_own_ring) {
> >   		if (vq->packed_ring) {
> >   			vring_free_queue(vq->vq.vdev,
> > @@ -2480,6 +2476,25 @@ void vring_del_virtqueue(struct virtqueue *_vq)
> >   		kfree(vq->split.desc_state);
> >   		kfree(vq->split.desc_extra);
> >   	}
> > +}
> > +
> > +static void vring_free(struct virtqueue *vq)
> > +{
> > +	__vring_free(vq);
> > +	vq->reset = VIRTIO_VQ_RESET_STEP_VRING_RELEASE;
> > +}
> > +
> > +void vring_del_virtqueue(struct virtqueue *_vq)
> > +{
> > +	struct vring_virtqueue *vq = to_vvq(_vq);
> > +
> > +	spin_lock(&vq->vq.vdev->vqs_list_lock);
> > +	list_del(&_vq->list);
> > +	spin_unlock(&vq->vq.vdev->vqs_list_lock);
> > +
> > +	if (_vq->reset != VIRTIO_VQ_RESET_STEP_VRING_RELEASE)
> > +		__vring_free(_vq);
> > +
> >   	kfree(vq);
> >   }
> >   EXPORT_SYMBOL_GPL(vring_del_virtqueue);
> > diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> > index d59adc4be068..e3714e6db330 100644
> > --- a/include/linux/virtio.h
> > +++ b/include/linux/virtio.h
> > @@ -10,6 +10,13 @@
> >   #include <linux/mod_devicetable.h>
> >   #include <linux/gfp.h>
> >
> > +enum virtio_vq_reset_step {
> > +	VIRTIO_VQ_RESET_STEP_NONE,
> > +	VIRTIO_VQ_RESET_STEP_DEVICE,
> > +	VIRTIO_VQ_RESET_STEP_VRING_RELEASE,
> > +	VIRTIO_VQ_RESET_STEP_VRING_ATTACH,
> > +};
>
>
> This part looks not related to the subject.
>
> And it needs detail documentation on this.
>
> But I wonder how useful it is, anyway we can check the reset status via
> transport specific way and in the future we may want to do more than
> just resizing (e.g PASID).


I will try and remove it from here.

Thanks.

>
> Thanks
>
>
> > +
> >   /**
> >    * virtqueue - a queue to register buffers for sending or receiving.
> >    * @list: the chain of virtqueues for this device
> > @@ -33,6 +40,7 @@ struct virtqueue {
> >   	unsigned int num_free;
> >   	unsigned int num_max;
> >   	void *priv;
> > +	enum virtio_vq_reset_step reset;
> >   };
> >
> >   int virtqueue_add_outbuf(struct virtqueue *vq,
>