xen: Make xen-blkfront write its protocol ABI to xenstore

Frontends are expected to write their protocol ABI to xenstore.  Since
the protocol ABI defaults to the backend's native ABI, things work
fine without that as long as the frontend's native ABI is identical to
the backend's native ABI.  This is not the case for xen-blkfront
running 32-on-64, because its ABI differs between 32 and 64 bit, and
thus needs this fix.

Based on http://xenbits.xensource.com/xen-unstable.hg?rev/c545932a18f3
and http://xenbits.xensource.com/xen-unstable.hg?rev/ffe52263b430 by
Gerd Hoffmann <kraxel@suse.de>

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 9c6f3f99208d..2e7c81e3f36a 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -47,6 +47,7 @@
 
 #include <xen/interface/grant_table.h>
 #include <xen/interface/io/blkif.h>
+#include <xen/interface/io/protocols.h>
 
 #include <asm/xen/hypervisor.h>
 
@@ -614,6 +615,12 @@ again:
                 message = "writing event-channel";
                 goto abort_transaction;
         }
+        err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
+                            XEN_IO_PROTO_ABI_NATIVE);
+        if (err) {
+                message = "writing protocol";
+                goto abort_transaction;
+        }
 
         err = xenbus_transaction_end(xbt, 0);
         if (err) {