[Xen-devel] [PATCHv1] xen-blkback: default to X86_32 ABI on x86

[David Vrabel <david.vrabel@xxxxxxxxxx>]

Prior to the existance of 64-bit backends using the X86_64 ABI,
frontends used the X86_32 ABI.  These old frontends do not specify the
ABI and when used with a 64-bit backend do not work.

On x86, default to the X86_32 ABI if one is not specified.  Backends
on ARM continue to default to their NATIVE ABI.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 drivers/block/xen-blkback/common.h |    9 +++++++++
 drivers/block/xen-blkback/xenbus.c |    4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkback/common.h 
b/drivers/block/xen-blkback/common.h
index f65b807..78b0411 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -214,6 +214,15 @@ enum blkif_protocol {
        BLKIF_PROTOCOL_X86_64 = 3,
 };
 
+/*
+ * Default protocol if the frontend doesn't specify one.
+ */
+#ifdef CONFIG_X86
+#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_X86_32
+#else
+#  define BLKIF_PROTOCOL_DEFAULT BLKIF_PROTOCOL_NATIVE
+#endif
+
 struct xen_vbd {
        /* What the domain refers to this vbd as. */
        blkif_vdev_t            handle;
diff --git a/drivers/block/xen-blkback/xenbus.c 
b/drivers/block/xen-blkback/xenbus.c
index 630a489..e3afe97 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -868,11 +868,11 @@ static int connect_ring(struct backend_info *be)
                return err;
        }
 
-       be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
+       be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
        err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
                            "%63s", protocol, NULL);
        if (err)
-               strcpy(protocol, "unspecified, assuming native");
+               strcpy(protocol, "unspecified, assuming default");
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
                be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
        else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
-- 
1.7.10.4


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