vDPA: report virtio-block max segment size to user space

This commit allows reporting the max size of any
single segment of virtio-block devices to user space.
Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Message-Id: <20240218185606.13509-3-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa.c

@@ -956,6 +956,20 @@ vdpa_dev_blk_capacity_config_fill(struct sk_buff *msg,
 				 val_u64, VDPA_ATTR_PAD);
 }
 
+static int
+vdpa_dev_blk_seg_size_config_fill(struct sk_buff *msg, u64 features,
+				  const struct virtio_blk_config *config)
+{
+	u32 val_u32;
+
+	if ((features & BIT_ULL(VIRTIO_BLK_F_SIZE_MAX)) == 0)
+		return 0;
+
+	val_u32 = __virtio32_to_cpu(true, config->size_max);
+
+	return nla_put_u32(msg, VDPA_ATTR_DEV_BLK_CFG_SEG_SIZE, val_u32);
+}
+
 static int vdpa_dev_blk_config_fill(struct vdpa_device *vdev,
 				    struct sk_buff *msg)
 {
@@ -973,6 +987,9 @@ static int vdpa_dev_blk_config_fill(struct vdpa_device *vdev,
 	if (vdpa_dev_blk_capacity_config_fill(msg, &config))
 		return -EMSGSIZE;
 
+	if (vdpa_dev_blk_seg_size_config_fill(msg, features_device, &config))
+		return -EMSGSIZE;
+
 	return 0;
 }
 

include/uapi/linux/vdpa.h

@@ -57,6 +57,7 @@ enum vdpa_attr {
 	VDPA_ATTR_DEV_FEATURES,                 /* u64 */
 
 	VDPA_ATTR_DEV_BLK_CFG_CAPACITY,		/* u64 */
+	VDPA_ATTR_DEV_BLK_CFG_SEG_SIZE,		/* u32 */
 
 	/* new attributes must be added above here */
 	VDPA_ATTR_MAX,