virtio-pci-modern: introduce helper for getting queue nums

stable inclusion
from stable-v5.12
commit 6e52fc44
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6e52fc446d32a82936f05106ffeef5cf8529e6c4

----------------------------------------------------------------------

This patch introduces helper for getting queue num of modern device.
Signed-off-by: NJason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210104065503.199631-14-jasowang@redhat.comSigned-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NPengyuan Zhao <zhaopengyuan@hisilicon.com>

drivers/virtio/virtio_pci_modern.c

@@ -292,6 +292,17 @@ static u16 vp_modern_get_queue_size(struct virtio_pci_modern_device *mdev,
 
 }
 
+/*
+ * vp_modern_get_num_queues - get the number of virtqueues
+ * @mdev: the modern virtio-pci device
+ *
+ * Returns the number of virtqueues
+ */
+static u16 vp_modern_get_num_queues(struct virtio_pci_modern_device *mdev)
+{
+	return vp_ioread16(&mdev->common->num_queues);
+}
+
 /* virtio config->finalize_features() implementation */
 static int vp_finalize_features(struct virtio_device *vdev)
 {
@@ -510,7 +521,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
 	u16 num, off;
 	int err;
 
-	if (index >= vp_ioread16(&cfg->num_queues))
+	if (index >= vp_modern_get_num_queues(mdev))
 		return ERR_PTR(-ENOENT);
 
 	/* Select the queue we're interested in */