Re: [PATCH v7 05/26] virtio_ring: split: extract the logic of init vq and attach vring

On Wed, 9 Mar 2022 15:36:59 +0800, Jason Wang [off-list ref] wrote:

在 2022/3/8 下午8:34, Xuan Zhuo 写道:

quoted

Split the logic of split assignment vq into three parts.

1. The assignment passed from the function parameter
2. The part that attaches vring to vq. -- __vring_virtqueue_attach_split()
3. The part that initializes vq to a fixed value --
    __vring_virtqueue_init_split()

This feature is required for subsequent virtuqueue reset vring

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
  drivers/virtio/virtio_ring.c | 111 +++++++++++++++++++++--------------
  1 file changed, 67 insertions(+), 44 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d32793615451..dc6313b79305 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c

@@ -2196,34 +2196,40 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
  }
  EXPORT_SYMBOL_GPL(vring_interrupt);

-/* Only available for split ring */
-struct virtqueue *__vring_new_virtqueue(unsigned int index,
-					struct vring vring,
-					struct virtio_device *vdev,
-					bool weak_barriers,
-					bool context,
-					bool (*notify)(struct virtqueue *),
-					void (*callback)(struct virtqueue *),
-					const char *name)
+static int __vring_virtqueue_attach_split(struct vring_virtqueue *vq,
+					  struct virtio_device *vdev,
+					  struct vring vring)
  {
-	struct vring_virtqueue *vq;
+	vq->vq.num_free = vring.num;

-	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
-		return NULL;
+	vq->split.vring = vring;
+	vq->split.queue_dma_addr = 0;
+	vq->split.queue_size_in_bytes = 0;

-	vq = kmalloc(sizeof(*vq), GFP_KERNEL);
-	if (!vq)
-		return NULL;
+	vq->split.desc_state = kmalloc_array(vring.num,
+					     sizeof(struct vring_desc_state_split), GFP_KERNEL);
+	if (!vq->split.desc_state)
+		goto err_state;

+	vq->split.desc_extra = vring_alloc_desc_extra(vq, vring.num);
+	if (!vq->split.desc_extra)
+		goto err_extra;

So this contains stuffs more than just attach. I wonder if it's better
to split the allocation out to an dedicated helper (we have dedicated
helper to allocate vring).

I will try in next version.

Thanks.

Thanks

quoted

+
+	memset(vq->split.desc_state, 0, vring.num *
+	       sizeof(struct vring_desc_state_split));
+	return 0;
+
+err_extra:
+	kfree(vq->split.desc_state);
+err_state:
+	return -ENOMEM;
+}
+
+static void __vring_virtqueue_init_split(struct vring_virtqueue *vq,
+					 struct virtio_device *vdev)
+{
  	vq->packed_ring = false;
-	vq->vq.callback = callback;
-	vq->vq.vdev = vdev;
-	vq->vq.name = name;
-	vq->vq.num_free = vring.num;
-	vq->vq.index = index;
  	vq->we_own_ring = false;
-	vq->notify = notify;
-	vq->weak_barriers = weak_barriers;
  	vq->broken = false;
  	vq->last_used_idx = 0;
  	vq->event_triggered = false;

@@ -2234,50 +2240,67 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
  	vq->last_add_time_valid = false;
  #endif

-	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
-		!context;
  	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);

  	if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM))
  		vq->weak_barriers = false;

-	vq->split.queue_dma_addr = 0;
-	vq->split.queue_size_in_bytes = 0;
-
-	vq->split.vring = vring;
  	vq->split.avail_flags_shadow = 0;
  	vq->split.avail_idx_shadow = 0;

  	/* No callback?  Tell other side not to bother us. */
-	if (!callback) {
+	if (!vq->vq.callback) {
  		vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
  		if (!vq->event)
  			vq->split.vring.avail->flags = cpu_to_virtio16(vdev,
  					vq->split.avail_flags_shadow);
  	}

-	vq->split.desc_state = kmalloc_array(vring.num,
-			sizeof(struct vring_desc_state_split), GFP_KERNEL);
-	if (!vq->split.desc_state)
-		goto err_state;
-
-	vq->split.desc_extra = vring_alloc_desc_extra(vq, vring.num);
-	if (!vq->split.desc_extra)
-		goto err_extra;
-
  	/* Put everything in free lists. */
  	vq->free_head = 0;
-	memset(vq->split.desc_state, 0, vring.num *
-			sizeof(struct vring_desc_state_split));
+}
+
+/* Only available for split ring */
+struct virtqueue *__vring_new_virtqueue(unsigned int index,
+					struct vring vring,
+					struct virtio_device *vdev,
+					bool weak_barriers,
+					bool context,
+					bool (*notify)(struct virtqueue *),
+					void (*callback)(struct virtqueue *),
+					const char *name)
+{
+	struct vring_virtqueue *vq;
+	int err;
+
+	if (virtio_has_feature(vdev, VIRTIO_F_RING_PACKED))
+		return NULL;
+
+	vq = kmalloc(sizeof(*vq), GFP_KERNEL);
+	if (!vq)
+		return NULL;
+
+	vq->vq.callback = callback;
+	vq->vq.vdev = vdev;
+	vq->vq.name = name;
+	vq->vq.index = index;
+	vq->notify = notify;
+	vq->weak_barriers = weak_barriers;
+	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&
+		!context;
+
+	err = __vring_virtqueue_attach_split(vq, vdev, vring);
+	if (err)
+		goto err;
+
+	__vring_virtqueue_init_split(vq, vdev);

  	spin_lock(&vdev->vqs_list_lock);
  	list_add_tail(&vq->vq.list, &vdev->vqs);
  	spin_unlock(&vdev->vqs_list_lock);
-	return &vq->vq;

-err_extra:
-	kfree(vq->split.desc_state);
-err_state:
+	return &vq->vq;
+err:
  	kfree(vq);
  	return NULL;
  }