virtio: Don't expose legacy block features when VIRTIO_BLK_NO_LEGACY defined.

This allows modern implementations to ensure they don't use legacy
feature bits or SCSI commands (which are not used in v1.0 non-legacy).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

include/uapi/linux/virtio_blk.h

@@ -31,22 +31,25 @@
 #include <linux/virtio_types.h>
 
 /* Feature bits */
-#define VIRTIO_BLK_F_BARRIER	0	/* Does host support barriers? */
 #define VIRTIO_BLK_F_SIZE_MAX	1	/* Indicates maximum segment size */
 #define VIRTIO_BLK_F_SEG_MAX	2	/* Indicates maximum # of segments */
 #define VIRTIO_BLK_F_GEOMETRY	4	/* Legacy geometry available  */
 #define VIRTIO_BLK_F_RO		5	/* Disk is read-only */
 #define VIRTIO_BLK_F_BLK_SIZE	6	/* Block size of disk is available*/
-#define VIRTIO_BLK_F_SCSI	7	/* Supports scsi command passthru */
-#define VIRTIO_BLK_F_WCE	9	/* Writeback mode enabled after reset */
 #define VIRTIO_BLK_F_TOPOLOGY	10	/* Topology information is available */
-#define VIRTIO_BLK_F_CONFIG_WCE	11	/* Writeback mode available in config */
 #define VIRTIO_BLK_F_MQ		12	/* support more than one vq */
 
+/* Legacy feature bits */
+#ifndef VIRTIO_BLK_NO_LEGACY
+#define VIRTIO_BLK_F_BARRIER	0	/* Does host support barriers? */
+#define VIRTIO_BLK_F_SCSI	7	/* Supports scsi command passthru */
+#define VIRTIO_BLK_F_WCE	9	/* Writeback mode enabled after reset */
+#define VIRTIO_BLK_F_CONFIG_WCE	11	/* Writeback mode available in config */
 #ifndef __KERNEL__
 /* Old (deprecated) name for VIRTIO_BLK_F_WCE. */
 #define VIRTIO_BLK_F_FLUSH VIRTIO_BLK_F_WCE
 #endif
+#endif /* !VIRTIO_BLK_NO_LEGACY */
 
 #define VIRTIO_BLK_ID_BYTES	20	/* ID string length */
 
@@ -100,8 +103,10 @@ struct virtio_blk_config {
 #define VIRTIO_BLK_T_IN		0
 #define VIRTIO_BLK_T_OUT	1
 
+#ifndef VIRTIO_BLK_NO_LEGACY
 /* This bit says it's a scsi command, not an actual read or write. */
 #define VIRTIO_BLK_T_SCSI_CMD	2
+#endif /* VIRTIO_BLK_NO_LEGACY */
 
 /* Cache flush command */
 #define VIRTIO_BLK_T_FLUSH	4
@@ -109,8 +114,10 @@ struct virtio_blk_config {
 /* Get device ID command */
 #define VIRTIO_BLK_T_GET_ID    8
 
+#ifndef VIRTIO_BLK_NO_LEGACY
 /* Barrier before this op. */
 #define VIRTIO_BLK_T_BARRIER	0x80000000
+#endif /* !VIRTIO_BLK_NO_LEGACY */
 
 /* This is the first element of the read scatter-gather list. */
 struct virtio_blk_outhdr {
@@ -122,12 +129,14 @@ struct virtio_blk_outhdr {
 	__virtio64 sector;
 };
 
+#ifndef VIRTIO_BLK_NO_LEGACY
 struct virtio_scsi_inhdr {
 	__virtio32 errors;
 	__virtio32 data_len;
 	__virtio32 sense_len;
 	__virtio32 residual;
 };
+#endif /* !VIRTIO_BLK_NO_LEGACY */
 
 /* And this is the final byte of the write scatter-gather list. */
 #define VIRTIO_BLK_S_OK		0