xen/interface: re-define FRONT/BACK_RING_ATTACH() (1ee54195) · Commits · 戴 / test

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>

include/xen/interface/io/ring.h

+9 −20

Original line number	Diff line number	Diff line
		@@ -125,35 +125,24 @@ 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; \
		(_r)->nr_ents = __RING_SIZE(_s, __size); \
		(_r)->sring = (_s); \
		} while (0)
		#define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)

		/* 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; \
		#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); \
		} 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) \
		((_r)->nr_ents)

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