[PATCH v5 19/22] virtio: add helper virtio_set_max_ring_num()

Xuan Zhuo
2022-02-14T08:14:13Z

Added helper virtio_set_max_ring_num() to set the upper limit of ring
num when creating a virtqueue.

Can be used to limit ring num before find_vqs() call. Or change ring num
when re-enable reset queue.

Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
 drivers/virtio/virtio_ring.c  |  6 ++++++
 include/linux/virtio.h        |  1 +
 include/linux/virtio_config.h | 30 ++++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 1a123b5e5371..a77a82883e44 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -943,6 +943,9 @@ static struct virtqueue *vring_create_virtqueue_split(
 	size_t queue_size_in_bytes;
 	struct vring vring;

+	if (vdev->max_ring_num && num > vdev->max_ring_num)
+		num = vdev->max_ring_num;
+
 	/* We assume num is a power of 2. */
 	if (num & (num - 1)) {
 		dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
@@ -1692,6 +1695,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
 	dma_addr_t ring_dma_addr, driver_event_dma_addr, device_event_dma_addr;
 	size_t ring_size_in_bytes, event_size_in_bytes;

+	if (vdev->max_ring_num && num > vdev->max_ring_num)
+		num = vdev->max_ring_num;
+
 	ring_size_in_bytes = num * sizeof(struct vring_packed_desc);

 	ring = vring_alloc_queue(vdev, ring_size_in_bytes,
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 1153b093c53d..45525beb2ec4 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -127,6 +127,7 @@ struct virtio_device {
 	struct list_head vqs;
 	u64 features;
 	void *priv;
+	u16 max_ring_num;
 };

 static inline struct virtio_device *dev_to_virtio(struct device *_dev)
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index cd7f7f44ce38..d7cb2d0341ee 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -200,6 +200,36 @@ static inline bool virtio_has_dma_quirk(const struct
virtio_device *vdev)
 	return !virtio_has_feature(vdev, VIRTIO_F_ACCESS_PLATFORM);
 }

+/**
+ * virtio_set_max_ring_num - set max ring num
+ * @vdev: the device
+ * @num: max ring num. Zero clear the limit.
+ *
+ * When creating a virtqueue, use this value as the upper limit of ring num.
+ *
+ * Returns 0 on success or error status
+ */
+static inline
+int virtio_set_max_ring_num(struct virtio_device *vdev, u16 num)
+{
+	if (!num) {
+		vdev->max_ring_num = num;
+		return 0;
+	}
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+		if (!is_power_of_2(num)) {
+			num = __rounddown_pow_of_two(num);
+
+			if (!num)
+				return -EINVAL;
+		}
+	}
+
+	vdev->max_ring_num = num;
+	return 0;
+}
+
 static inline
 struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
 					vq_callback_t *c, const char *n)
--
2.31.0