virtio-scsi.h: Add virtio_scsi_cmd_req_pi + VIRTIO_SCSI_F_T10_PI bits

This patch adds a virtio_scsi_cmd_req_pi header as recommened by
Paolo that contains pi_bytesout + pi_bytesin elements used for
signaling when protection information buffers (in bytes) are
expected to preceed the data payload buffers.

Also add new VIRTIO_SCSI_F_T10_PI feature bit to be used to signal
host support.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sagi Grimberg <sagig@dev.mellanox.co.il>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

include/linux/virtio_scsi.h

@@ -35,11 +35,23 @@ struct virtio_scsi_cmd_req {
 	u8 lun[8];		/* Logical Unit Number */
 	u64 tag;		/* Command identifier */
 	u8 task_attr;		/* Task attribute */
-	u8 prio;
+	u8 prio;		/* SAM command priority field */
 	u8 crn;
 	u8 cdb[VIRTIO_SCSI_CDB_SIZE];
 } __packed;
 
+/* SCSI command request, followed by protection information */
+struct virtio_scsi_cmd_req_pi {
+	u8 lun[8];		/* Logical Unit Number */
+	u64 tag;		/* Command identifier */
+	u8 task_attr;		/* Task attribute */
+	u8 prio;		/* SAM command priority field */
+	u8 crn;
+	u32 pi_bytesout;	/* DataOUT PI Number of bytes */
+	u32 pi_bytesin;		/* DataIN PI Number of bytes */
+	u8 cdb[VIRTIO_SCSI_CDB_SIZE];
+} __packed;
+
 /* Response, followed by sense data and data-in */
 struct virtio_scsi_cmd_resp {
 	u32 sense_len;		/* Sense data length */
@@ -97,6 +109,7 @@ struct virtio_scsi_config {
 #define VIRTIO_SCSI_F_INOUT                    0
 #define VIRTIO_SCSI_F_HOTPLUG                  1
 #define VIRTIO_SCSI_F_CHANGE                   2
+#define VIRTIO_SCSI_F_T10_PI                   3
 
 /* Response codes */
 #define VIRTIO_SCSI_S_OK                       0