[Xen-devel] [PATCH][XEN] PV blk backend: Make 32bit PV guests work on 64bit PV Dom0

[Christoph Egger <Christoph.Egger@xxxxxxx>]

Hi,

Attached patch makes the PV block driver for 32bit PV guests working on
64bit PV Dom0.

In the io/blkif.h,  the 'id' field of
struct blkif_request is 64bit, but on a LP32 system it's aligned on 
32bits, while it'll be aligned to 64bits on a LP64 system. So on LP64 there'll 
be 4 bytes of padding between handle and id. The same is true for
struct blkif_response: it's 11 bytes long, so will be aligned differently
in the ring between a 32 and 64bit systems.

In order to fix this, attached patch introduces in the public headers,
blkif_request/blkif_response, blkif_x86_32_request/blkif_x86_32_response
and blkif_x86_64_request/blkif_x86_64_response.
NetBSD is doing so io/blkif.h in the public headers, while Linux
does so in include/xen/blkif.h in the linux sources. But the result is
the same ...

Successfully tested with the combinations:

64bit Dom0                32bit PAE PV guest
NetBSD                       Linux
Linux                            NetBSD

The combinations 64bit Dom0, 64bit PV DomU works with and without this patch.

Signed-off-by: Christoph Egger <Christoph.Egger@xxxxxxx>


-- 
AMD Saxony, Dresden, Germany
Operating System Research Center

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