storvsc: force SPC-3 compliance on win8 and win8 r2 hosts

On win8 and win8 r2 hosts force SPC-3 compliance for MSFT virtual disks.
Ubuntu has been carrying a similar patch outside the tree for a while now.
Starting with win10, the host will support SPC-3 compliance. Based on all
the testing that has been done on win8 and win8 r2 hosts, we are comfortable
claiming SPC-3 compliance on these hosts as well. This will enable TRIM
support on these hosts.

Suggested by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: NLong Li <longli@microsoft.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

drivers/scsi/storvsc_drv.c

@@ -1394,6 +1394,19 @@ static int storvsc_device_configure(struct scsi_device *sdevice)
 	 */
 	sdevice->sdev_bflags |= msft_blist_flags;
 
+	/*
+	 * If the host is WIN8 or WIN8 R2, claim conformance to SPC-3
+	 * if the device is a MSFT virtual device.
+	 */
+	if (!strncmp(sdevice->vendor, "Msft", 4)) {
+		switch (vmbus_proto_version) {
+		case VERSION_WIN8:
+		case VERSION_WIN8_1:
+			sdevice->scsi_level = SCSI_SPC_3;
+			break;
+		}
+	}
+
 	return 0;
 }