xen-blk{front/back}: remove broken FreeBSD extensions

The FreeBSD extension adds a new request type, called blkif_segment_block
which has a size of 112bytes for both i386 and amd64. This is fine on
amd64, since requests have a size of 112B there also. But this is not true
for i386, where requests have a size of 108B. So on i386 we basically
overrun the ring slot when queuing a request of type blkif_segment_block_t,
which is very bad.

Remove this extension (including a cleanup of the public blkif.h header
file) from blkfront and blkback.

Sponsored by: Citrix Systems R&D
Tested-by: cperciva

2 files changed, 6 insertions, 44 deletions

diff --git a/sys/xen/blkif.h b/sys/xen/blkif.h
index 48b71ea..8a19d5d 100644
--- a/sys/xen/blkif.h
+++ b/sys/xen/blkif.h
@@ -46,7 +46,7 @@ struct blkif_x86_32_request {
 	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_HEADER_BLOCK];
+	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
 struct blkif_x86_32_response {
 	uint64_t        id;              /* copied from request */
@@ -64,7 +64,7 @@ struct blkif_x86_64_request {
 	blkif_vdev_t   handle;       /* only for read/write requests         */
 	uint64_t       __attribute__((__aligned__(8))) id;
 	blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
-	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK];
+	struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
 struct blkif_x86_64_response {
 	uint64_t       __attribute__((__aligned__(8))) id;
@@ -114,7 +114,7 @@ enum blkif_protocol {
 
 static void inline blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_request_t *src)
 {
-	int i, n = BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK;
+	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 	dst->operation = src->operation;
 	dst->nr_segments = src->nr_segments;
 	dst->handle = src->handle;
@@ -129,7 +129,7 @@ static void inline blkif_get_x86_32_req(blkif_request_t *dst, blkif_x86_32_reque
 
 static void inline blkif_get_x86_64_req(blkif_request_t *dst, blkif_x86_64_request_t *src)
 {
-	int i, n = BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK;
+	int i, n = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 	dst->operation = src->operation;
 	dst->nr_segments = src->nr_segments;
 	dst->handle = src->handle;
diff --git a/sys/xen/interface/io/blkif.h b/sys/xen/interface/io/blkif.h
index 9155662..b725776 100644
--- a/sys/xen/interface/io/blkif.h
+++ b/sys/xen/interface/io/blkif.h
@@ -457,21 +457,9 @@
 #define BLKIF_OP_DISCARD           5
 
 /*
- * Maximum scatter/gather segments associated with a request header block.
- * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE.
- * NB. This could be 12 if the ring indexes weren't stored in the same page.
- */
-#define BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK  11
-
-/*
- * Maximum scatter/gather segments associated with a segment block.
- */
-#define BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK 14
-
-/*
  * Maximum scatter/gather segments per request (header + segment blocks).
  */
-#define BLKIF_MAX_SEGMENTS_PER_REQUEST 255
+#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 
 /*
  * NB. first_sect and last_sect in blkif_request_segment, as well as
@@ -512,22 +500,11 @@ struct blkif_request {
     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)  */
-    blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK];
+    blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 };
 typedef struct blkif_request blkif_request_t;
 
 /*
- * A segment block is a ring request structure that contains only
- * segment data.
- *
- * sizeof(struct blkif_segment_block) <= sizeof(struct blkif_request)
- */
-struct blkif_segment_block {
-    blkif_request_segment_t seg[BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK];
-};
-typedef struct blkif_segment_block blkif_segment_block_t;
-
-/*
  * Cast to this structure when blkif_request.operation == BLKIF_OP_DISCARD
  * sizeof(struct blkif_request_discard) <= sizeof(struct blkif_request)
  */
@@ -564,21 +541,6 @@ typedef struct blkif_response blkif_response_t;
  */
 DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
 
-/*
- * Index to, and treat as a segment block, an entry in the ring.
- */
-#define BLKRING_GET_SEG_BLOCK(_r, _idx)                                 \
-    (((blkif_segment_block_t *)RING_GET_REQUEST(_r, _idx))->seg)
-
-/*
- * The number of ring request blocks required to handle an I/O
- * request containing _segs segments.
- */
-#define BLKIF_SEGS_TO_BLOCKS(_segs)                                     \
-    ((((_segs - BLKIF_MAX_SEGMENTS_PER_HEADER_BLOCK)                    \
-     + (BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK - 1))                      \
-    / BLKIF_MAX_SEGMENTS_PER_SEGMENT_BLOCK) + /*header_block*/1)
-
 #define VDISK_CDROM        0x1
 #define VDISK_REMOVABLE    0x2
 #define VDISK_READONLY     0x4