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

[Christoph Egger <Christoph.Egger@amd.com>]

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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@amd.com>


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

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   Dr. Hans-R. Deppe, Thomas McCoy

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diff -r 37fae02cc335 xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h	Fri Jul 25 15:03:03 2008 +0100
+++ b/xen/include/public/io/blkif.h	Mon Jul 28 11:02:12 2008 +0200
@@ -91,6 +91,8 @@ struct blkif_request_segment {
     uint8_t     first_sect, last_sect;
 };
 
+/* native-type requests/responses (always used in frontends ) */
+
 struct blkif_request {
     uint8_t        operation;    /* BLKIF_OP_???                         */
     uint8_t        nr_segments;  /* number of segments                   */
@@ -108,6 +110,44 @@ struct blkif_response {
 };
 typedef struct blkif_response blkif_response_t;
 
+/* i386 requests/responses */
+struct blkif_x86_32_request {
+    uint8_t        operation;    /* BLKIF_OP_???                         */
+    uint8_t        nr_segments;  /* number of segments                   */
+    blkif_vdev_t   handle;       /* only for read/write requests         */
+    uint64_t       id;           /* private guest value, echoed in resp  */
+    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
+    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+} /* __packed */;
+typedef struct blkif_x86_32_request blkif_x86_32_request_t;
+
+struct blkif_x86_32_response {
+    uint64_t        id;              /* copied from request */
+    uint8_t         operation;       /* copied from request */
+    uint8_t         _pad; 
+    int16_t         status;          /* BLKIF_RSP_???       */
+} /* __packed */;
+typedef struct blkif_x86_32_response blkif_x86_32_response_t;
+
+/* amd64-type requests/responses (always used in frontends ) */
+
+struct blkif_x86_64_request {
+    uint8_t          operation;    /* BLKIF_OP_???                         */
+    uint8_t          nr_segments;  /* number of segments                   */
+    blkif_vdev_t     handle;       /* only for read/write requests         */
+    uint64_aligned_t id;/* private guest value, echoed in resp  */
+    blkif_sector_t   sector_number;/* start sector idx on disk (r/w only)  */
+    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+};
+typedef struct blkif_x86_64_request blkif_x86_64_request_t;
+
+struct blkif_x86_64_response {
+    uint64_aligned_t id; /* copied from request */
+    uint8_t          operation;       /* copied from request */
+    int16_t          status;          /* BLKIF_RSP_???       */
+};
+typedef struct blkif_x86_64_response blkif_x86_64_response_t;
+
 /*
  * STATUS RETURN CODES.
  */
@@ -123,6 +163,15 @@ typedef struct blkif_response blkif_resp
  */
 
 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
+DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request, struct blkif_x86_32_response);
+DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request, struct blkif_x86_64_response);
+
+union blkif_back_ring_proto {
+	blkif_back_ring_t ring_n; /* native/common members */
+	blkif_x86_32_back_ring_t ring_32;
+	blkif_x86_64_back_ring_t ring_64;
+};
+typedef union blkif_back_ring_proto blkif_back_ring_proto_t;
 
 #define VDISK_CDROM        0x1
 #define VDISK_REMOVABLE    0x2

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