Date:   Wed, 13 Apr 2022 11:23:30 +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, 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,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v9 12/32] virtio_ring: packed: extract the logic of alloc queue

On Tue, 12 Apr 2022 14:28:24 +0800, Jason Wang <jasowang@...hat.com> wrote:
>
> 在 2022/4/6 上午11:43, Xuan Zhuo 写道:
> > Separate the logic of packed to create vring queue.
> >
> > For the convenience of passing parameters, add a structure
> > vring_packed.
> >
> > This feature is required for subsequent virtuqueue reset vring.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > ---
> >   drivers/virtio/virtio_ring.c | 70 ++++++++++++++++++++++++++++--------
> >   1 file changed, 56 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > index 33864134a744..ea451ae2aaef 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -1817,19 +1817,17 @@ static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int num)
> >   	return desc_extra;
> >   }
> >
> > -static struct virtqueue *vring_create_virtqueue_packed(
> > -	unsigned int index,
> > -	unsigned int num,
> > -	unsigned int vring_align,
> > -	struct virtio_device *vdev,
> > -	bool weak_barriers,
> > -	bool may_reduce_num,
> > -	bool context,
> > -	bool (*notify)(struct virtqueue *),
> > -	void (*callback)(struct virtqueue *),
> > -	const char *name)
> > +static int vring_alloc_queue_packed(struct virtio_device *vdev,
> > +				    u32 num,
> > +				    struct vring_packed_desc **_ring,
> > +				    struct vring_packed_desc_event **_driver,
> > +				    struct vring_packed_desc_event **_device,
> > +				    dma_addr_t *_ring_dma_addr,
> > +				    dma_addr_t *_driver_event_dma_addr,
> > +				    dma_addr_t *_device_event_dma_addr,
> > +				    size_t *_ring_size_in_bytes,
> > +				    size_t *_event_size_in_bytes)
> >   {
> > -	struct vring_virtqueue *vq;
> >   	struct vring_packed_desc *ring;
> >   	struct vring_packed_desc_event *driver, *device;
> >   	dma_addr_t ring_dma_addr, driver_event_dma_addr, device_event_dma_addr;
> > @@ -1857,6 +1855,52 @@ static struct virtqueue *vring_create_virtqueue_packed(
> >   	if (!device)
> >   		goto err_device;
> >
> > +	*_ring                   = ring;
> > +	*_driver                 = driver;
> > +	*_device                 = device;
> > +	*_ring_dma_addr          = ring_dma_addr;
> > +	*_driver_event_dma_addr  = driver_event_dma_addr;
> > +	*_device_event_dma_addr  = device_event_dma_addr;
> > +	*_ring_size_in_bytes     = ring_size_in_bytes;
> > +	*_event_size_in_bytes    = event_size_in_bytes;
>
>
> I wonder if we can simply factor out split and packed from struct
> vring_virtqueue:
>
> struct vring_virtqueue {
>      union {
>          struct {} split;
>          struct {} packed;
>      };
> };
>
> to
>
> struct vring_virtqueue_split {};
> struct vring_virtqueue_packed {};
>
> Then we can do things like:
>
> vring_create_virtqueue_packed(struct virtio_device *vdev, u32 num,
> struct vring_virtqueue_packed *packed);
>
> and
>
> vring_vritqueue_attach_packed(struct vring_virtqueue *vq, struct
> vring_virtqueue_packed packed);

This idea is very similar to my previous idea, just without introducing a new
structure.

I'd be more than happy to revise this.

Thanks.


>
> Thanks
>
>
> > +
> > +	return 0;
> > +
> > +err_device:
> > +	vring_free_queue(vdev, event_size_in_bytes, driver, driver_event_dma_addr);
> > +
> > +err_driver:
> > +	vring_free_queue(vdev, ring_size_in_bytes, ring, ring_dma_addr);
> > +
> > +err_ring:
> > +	return -ENOMEM;
> > +}
> > +
> > +static struct virtqueue *vring_create_virtqueue_packed(
> > +	unsigned int index,
> > +	unsigned int num,
> > +	unsigned int vring_align,
> > +	struct virtio_device *vdev,
> > +	bool weak_barriers,
> > +	bool may_reduce_num,
> > +	bool context,
> > +	bool (*notify)(struct virtqueue *),
> > +	void (*callback)(struct virtqueue *),
> > +	const char *name)
> > +{
> > +	dma_addr_t ring_dma_addr, driver_event_dma_addr, device_event_dma_addr;
> > +	struct vring_packed_desc_event *driver, *device;
> > +	size_t ring_size_in_bytes, event_size_in_bytes;
> > +	struct vring_packed_desc *ring;
> > +	struct vring_virtqueue *vq;
> > +
> > +	if (vring_alloc_queue_packed(vdev, num, &ring, &driver, &device,
> > +				     &ring_dma_addr, &driver_event_dma_addr,
> > +				     &device_event_dma_addr,
> > +				     &ring_size_in_bytes,
> > +				     &event_size_in_bytes))
> > +		goto err_ring;
> > +
> >   	vq = kmalloc(sizeof(*vq), GFP_KERNEL);
> >   	if (!vq)
> >   		goto err_vq;
> > @@ -1939,9 +1983,7 @@ static struct virtqueue *vring_create_virtqueue_packed(
> >   	kfree(vq);
> >   err_vq:
> >   	vring_free_queue(vdev, event_size_in_bytes, device, device_event_dma_addr);
> > -err_device:
> >   	vring_free_queue(vdev, event_size_in_bytes, driver, driver_event_dma_addr);
> > -err_driver:
> >   	vring_free_queue(vdev, ring_size_in_bytes, ring, ring_dma_addr);
> >   err_ring:
> >   	return NULL;
>

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