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xen/interface: re-define FRONT/BACK_RING_ATTACH()

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Currently these macros are defined to re-initialize a front/back ring
(respectively) to values read from the shared ring in such a way that any
requests/responses that are added to the shared ring whilst the front/back
is detached will be skipped over. This, in general, is not a desirable
semantic since most frontend implementations will eventually block waiting
for a response which would either never appear or never be processed.

Since the macros are currently unused, take this opportunity to re-define
them to re-initialize a front/back ring using specified values. This also
allows FRONT/BACK_RING_INIT() to be re-defined in terms of
FRONT/BACK_RING_ATTACH() using a specified value of 0.

NOTE: BACK_RING_ATTACH() will be used directly in a subsequent patch.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Paul Durrant 2019-12-11 15:29:55 +00:00 committed by Juergen Gross
parent 672b7763cb
commit 1ee54195a3
1 changed files with 9 additions and 20 deletions
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29
include/xen/interface/io/ring.h
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@ -125,34 +125,23 @@ struct __name##_back_ring { \
memset((_s)->pad, 0, sizeof((_s)->pad)); \
} while(0)
#define FRONT_RING_INIT(_r, _s, __size) do { \
(_r)->req_prod_pvt = 0; \
(_r)->rsp_cons = 0; \
#define FRONT_RING_ATTACH(_r, _s, _i, __size) do { \
(_r)->req_prod_pvt = (_i); \
(_r)->rsp_cons = (_i); \
(_r)->nr_ents = __RING_SIZE(_s, __size); \
(_r)->sring = (_s); \
} while (0)
#define BACK_RING_INIT(_r, _s, __size) do { \
(_r)->rsp_prod_pvt = 0; \
(_r)->req_cons = 0; \
#define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)
#define BACK_RING_ATTACH(_r, _s, _i, __size) do { \
(_r)->rsp_prod_pvt = (_i); \
(_r)->req_cons = (_i); \
(_r)->nr_ents = __RING_SIZE(_s, __size); \
(_r)->sring = (_s); \
} while (0)
/* Initialize to existing shared indexes -- for recovery */
#define FRONT_RING_ATTACH(_r, _s, __size) do { \
(_r)->sring = (_s); \
(_r)->req_prod_pvt = (_s)->req_prod; \
(_r)->rsp_cons = (_s)->rsp_prod; \
(_r)->nr_ents = __RING_SIZE(_s, __size); \
} while (0)
#define BACK_RING_ATTACH(_r, _s, __size) do { \
(_r)->sring = (_s); \
(_r)->rsp_prod_pvt = (_s)->rsp_prod; \
(_r)->req_cons = (_s)->req_prod; \
(_r)->nr_ents = __RING_SIZE(_s, __size); \
} while (0)
#define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)
/* How big is this ring? */
#define RING_SIZE(_r) \