virtio_ring: introduce virtqueue_resize()

Introduce virtqueue_resize() to implement the resize of vring.
Based on these, the driver can dynamically adjust the size of the vring.
For example: ethtool -G.

virtqueue_resize() implements resize based on the vq reset function. In
case of failure to allocate a new vring, it will give up resize and use
the original vring.

During this process, if the re-enable reset vq fails, the vq can no
longer be used. Although the probability of this situation is not high.

The parameter recycle is used to recycle the buffer that is no longer
used.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220801063902.129329-25-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index bea5a3448217c5692069b79177ced2e60063fe10..6447a09e2e381a798b8da890dce4376e865183b6 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2539,6 +2539,75 @@ struct virtqueue *vring_create_virtqueue(
 }
 EXPORT_SYMBOL_GPL(vring_create_virtqueue);
 
+/**
+ * virtqueue_resize - resize the vring of vq
+ * @_vq: the struct virtqueue we're talking about.
+ * @num: new ring num
+ * @recycle: callback for recycle the useless buffer
+ *
+ * When it is really necessary to create a new vring, it will set the current vq
+ * into the reset state. Then call the passed callback to recycle the buffer
+ * that is no longer used. Only after the new vring is successfully created, the
+ * old vring will be released.
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error.
+ * 0: success.
+ * -ENOMEM: Failed to allocate a new ring, fall back to the original ring size.
+ *  vq can still work normally
+ * -EBUSY: Failed to sync with device, vq may not work properly
+ * -ENOENT: Transport or device not supported
+ * -E2BIG/-EINVAL: num error
+ * -EPERM: Operation not permitted
+ *
+ */
+int virtqueue_resize(struct virtqueue *_vq, u32 num,
+                    void (*recycle)(struct virtqueue *vq, void *buf))
+{
+       struct vring_virtqueue *vq = to_vvq(_vq);
+       struct virtio_device *vdev = vq->vq.vdev;
+       void *buf;
+       int err;
+
+       if (!vq->we_own_ring)
+               return -EPERM;
+
+       if (num > vq->vq.num_max)
+               return -E2BIG;
+
+       if (!num)
+               return -EINVAL;
+
+       if ((vq->packed_ring ? vq->packed.vring.num : vq->split.vring.num) == num)
+               return 0;
+
+       if (!vdev->config->disable_vq_and_reset)
+               return -ENOENT;
+
+       if (!vdev->config->enable_vq_after_reset)
+               return -ENOENT;
+
+       err = vdev->config->disable_vq_and_reset(_vq);
+       if (err)
+               return err;
+
+       while ((buf = virtqueue_detach_unused_buf(_vq)) != NULL)
+               recycle(_vq, buf);
+
+       if (vq->packed_ring)
+               err = virtqueue_resize_packed(_vq, num);
+       else
+               err = virtqueue_resize_split(_vq, num);
+
+       if (vdev->config->enable_vq_after_reset(_vq))
+               return -EBUSY;
+
+       return err;
+}
+EXPORT_SYMBOL_GPL(virtqueue_resize);
+
 /* Only available for split ring */
 struct virtqueue *vring_new_virtqueue(unsigned int index,
                                      unsigned int num,

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 129bde7521e301324dcf6cd4dabe72d306ee7af4..62e31bca56024b0d8df4511faf3ac04ce6303516 100644 (file)
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -91,6 +91,9 @@ dma_addr_t virtqueue_get_desc_addr(struct virtqueue *vq);
 dma_addr_t virtqueue_get_avail_addr(struct virtqueue *vq);
 dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq);
 
+int virtqueue_resize(struct virtqueue *vq, u32 num,
+                    void (*recycle)(struct virtqueue *vq, void *buf));
+
 /**
  * virtio_device - representation of a device using virtio
  * @index: unique position on the virtio bus