xen: add block device backend driver. (Gerd Hoffmann)

This patch adds a block device backend driver to qemu.  It is a pure
userspace implemention using the gntdev interface.  It uses "qdisk" as
backend name in xenstore so it doesn't interfere with the other existing
backends (blkback aka "vbd" and tapdisk aka "tap").

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7223 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/vl.c b/vl.c
index 7b0e0d5..1342665 100644
--- a/vl.c
+++ b/vl.c
@@ -2373,7 +2373,10 @@
         } else if (!strcmp(buf, "virtio")) {
             type = IF_VIRTIO;
             max_devs = 0;
-        } else {
+	} else if (!strcmp(buf, "xen")) {
+	    type = IF_XEN;
+            max_devs = 0;
+	} else {
             fprintf(stderr, "qemu: '%s' unsupported bus type '%s'\n", str, buf);
             return -1;
 	}
@@ -2587,6 +2590,7 @@
     switch(type) {
     case IF_IDE:
     case IF_SCSI:
+    case IF_XEN:
         switch(media) {
 	case MEDIA_DISK:
             if (cyls != 0) {