287 lines
10 KiB
C
287 lines
10 KiB
C
|
/******************************************************************************
|
||
|
|
* ring.h
|
||
|
|
*
|
||
|
|
* Shared producer-consumer ring macros.
|
||
|
|
*
|
||
|
|
* Tim Deegan and Andrew Warfield November 2004.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef __XEN_PUBLIC_IO_RING_H__
|
||
|
|
#define __XEN_PUBLIC_IO_RING_H__
|
||
|
|
|
||
|
|
typedef unsigned int RING_IDX;
|
||
|
|
|
||
|
|
/* Round a 32-bit unsigned constant down to the nearest power of two. */
|
||
|
|
#define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
|
||
|
|
#define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
|
||
|
|
#define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
|
||
|
|
#define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
|
||
|
|
#define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Calculate size of a shared ring, given the total available space for the
|
||
|
|
* ring and indexes (_sz), and the name tag of the request/response structure.
|
||
|
|
* A ring contains as many entries as will fit, rounded down to the nearest
|
||
|
|
* power of two (so we can mask with (size-1) to loop around).
|
||
|
|
*/
|
||
|
|
#define __CONST_RING_SIZE(_s, _sz) \
|
||
|
|
(__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
|
||
|
|
sizeof(((struct _s##_sring *)0)->ring[0])))
|
||
|
|
|
||
|
|
/*
|
||
|
|
* The same for passing in an actual pointer instead of a name tag.
|
||
|
|
*/
|
||
|
|
#define __RING_SIZE(_s, _sz) \
|
||
|
|
(__RD32(((_sz) - (long)&(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Macros to make the correct C datatypes for a new kind of ring.
|
||
|
|
*
|
||
|
|
* To make a new ring datatype, you need to have two message structures,
|
||
|
|
* let's say struct request, and struct response already defined.
|
||
|
|
*
|
||
|
|
* In a header where you want the ring datatype declared, you then do:
|
||
|
|
*
|
||
|
|
* DEFINE_RING_TYPES(mytag, struct request, struct response);
|
||
|
|
*
|
||
|
|
* These expand out to give you a set of types, as you can see below.
|
||
|
|
* The most important of these are:
|
||
|
|
*
|
||
|
|
* struct mytag_sring - The shared ring.
|
||
|
|
* struct mytag_front_ring - The 'front' half of the ring.
|
||
|
|
* struct mytag_back_ring - The 'back' half of the ring.
|
||
|
|
*
|
||
|
|
* To initialize a ring in your code you need to know the location and size
|
||
|
|
* of the shared memory area (PAGE_SIZE, for instance). To initialise
|
||
|
|
* the front half:
|
||
|
|
*
|
||
|
|
* struct mytag_front_ring front_ring;
|
||
|
|
* SHARED_RING_INIT((struct mytag_sring *)shared_page);
|
||
|
|
* FRONT_RING_INIT(&front_ring, (struct mytag_sring *)shared_page,
|
||
|
|
* PAGE_SIZE);
|
||
|
|
*
|
||
|
|
* Initializing the back follows similarly (note that only the front
|
||
|
|
* initializes the shared ring):
|
||
|
|
*
|
||
|
|
* struct mytag_back_ring back_ring;
|
||
|
|
* BACK_RING_INIT(&back_ring, (struct mytag_sring *)shared_page,
|
||
|
|
* PAGE_SIZE);
|
||
|
|
*/
|
||
|
|
|
||
|
|
#define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
|
||
|
|
\
|
||
|
|
/* Shared ring entry */ \
|
||
|
|
union __name##_sring_entry { \
|
||
|
|
__req_t req; \
|
||
|
|
__rsp_t rsp; \
|
||
|
|
}; \
|
||
|
|
\
|
||
|
|
/* Shared ring page */ \
|
||
|
|
struct __name##_sring { \
|
||
|
|
RING_IDX req_prod, req_event; \
|
||
|
|
RING_IDX rsp_prod, rsp_event; \
|
||
|
|
uint8_t pad[48]; \
|
||
|
|
union __name##_sring_entry ring[1]; /* variable-length */ \
|
||
|
|
}; \
|
||
|
|
\
|
||
|
|
/* "Front" end's private variables */ \
|
||
|
|
struct __name##_front_ring { \
|
||
|
|
RING_IDX req_prod_pvt; \
|
||
|
|
RING_IDX rsp_cons; \
|
||
|
|
unsigned int nr_ents; \
|
||
|
|
struct __name##_sring *sring; \
|
||
|
|
}; \
|
||
|
|
\
|
||
|
|
/* "Back" end's private variables */ \
|
||
|
|
struct __name##_back_ring { \
|
||
|
|
RING_IDX rsp_prod_pvt; \
|
||
|
|
RING_IDX req_cons; \
|
||
|
|
unsigned int nr_ents; \
|
||
|
|
struct __name##_sring *sring; \
|
||
|
|
};
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Macros for manipulating rings.
|
||
|
|
*
|
||
|
|
* FRONT_RING_whatever works on the "front end" of a ring: here
|
||
|
|
* requests are pushed on to the ring and responses taken off it.
|
||
|
|
*
|
||
|
|
* BACK_RING_whatever works on the "back end" of a ring: here
|
||
|
|
* requests are taken off the ring and responses put on.
|
||
|
|
*
|
||
|
|
* N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
|
||
|
|
* This is OK in 1-for-1 request-response situations where the
|
||
|
|
* requestor (front end) never has more than RING_SIZE()-1
|
||
|
|
* outstanding requests.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Initialising empty rings */
|
||
|
|
#define SHARED_RING_INIT(_s) do { \
|
||
|
|
(_s)->req_prod = (_s)->rsp_prod = 0; \
|
||
|
|
(_s)->req_event = (_s)->rsp_event = 1; \
|
||
|
|
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; \
|
||
|
|
(_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)
|
||
|
|
|
||
|
|
/* 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)
|
||
|
|
|
||
|
|
/* How big is this ring? */
|
||
|
|
#define RING_SIZE(_r) \
|
||
|
|
((_r)->nr_ents)
|
||
|
|
|
||
|
|
/* Number of free requests (for use on front side only). */
|
||
|
|
#define RING_FREE_REQUESTS(_r) \
|
||
|
|
(RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
|
||
|
|
|
||
|
|
/* Test if there is an empty slot available on the front ring.
|
||
|
|
* (This is only meaningful from the front. )
|
||
|
|
*/
|
||
|
|
#define RING_FULL(_r) \
|
||
|
|
(RING_FREE_REQUESTS(_r) == 0)
|
||
|
|
|
||
|
|
/* Test if there are outstanding messages to be processed on a ring. */
|
||
|
|
#define RING_HAS_UNCONSUMED_RESPONSES(_r) \
|
||
|
|
((_r)->sring->rsp_prod - (_r)->rsp_cons)
|
||
|
|
|
||
|
|
#define RING_HAS_UNCONSUMED_REQUESTS(_r) \
|
||
|
|
({ \
|
||
|
|
unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
|
||
|
|
unsigned int rsp = RING_SIZE(_r) - \
|
||
|
|
((_r)->req_cons - (_r)->rsp_prod_pvt); \
|
||
|
|
req < rsp ? req : rsp; \
|
||
|
|
})
|
||
|
|
|
||
|
|
/* Direct access to individual ring elements, by index. */
|
||
|
|
#define RING_GET_REQUEST(_r, _idx) \
|
||
|
|
(&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Get a local copy of a request.
|
||
|
|
*
|
||
|
|
* Use this in preference to RING_GET_REQUEST() so all processing is
|
||
|
|
* done on a local copy that cannot be modified by the other end.
|
||
|
|
*
|
||
|
|
* Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this
|
||
|
|
* to be ineffective where _req is a struct which consists of only bitfields.
|
||
|
|
*/
|
||
|
|
#define RING_COPY_REQUEST(_r, _idx, _req) do { \
|
||
|
|
/* Use volatile to force the copy into _req. */ \
|
||
|
|
*(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#define RING_GET_RESPONSE(_r, _idx) \
|
||
|
|
(&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
|
||
|
|
|
||
|
|
/* Loop termination condition: Would the specified index overflow the ring? */
|
||
|
|
#define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
|
||
|
|
(((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
|
||
|
|
|
||
|
|
/* Ill-behaved frontend determination: Can there be this many requests? */
|
||
|
|
#define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
|
||
|
|
(((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
|
||
|
|
|
||
|
|
|
||
|
|
#define RING_PUSH_REQUESTS(_r) do { \
|
||
|
|
virt_wmb(); /* back sees requests /before/ updated producer index */ \
|
||
|
|
(_r)->sring->req_prod = (_r)->req_prod_pvt; \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#define RING_PUSH_RESPONSES(_r) do { \
|
||
|
|
virt_wmb(); /* front sees responses /before/ updated producer index */ \
|
||
|
|
(_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Notification hold-off (req_event and rsp_event):
|
||
|
|
*
|
||
|
|
* When queueing requests or responses on a shared ring, it may not always be
|
||
|
|
* necessary to notify the remote end. For example, if requests are in flight
|
||
|
|
* in a backend, the front may be able to queue further requests without
|
||
|
|
* notifying the back (if the back checks for new requests when it queues
|
||
|
|
* responses).
|
||
|
|
*
|
||
|
|
* When enqueuing requests or responses:
|
||
|
|
*
|
||
|
|
* Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
|
||
|
|
* is a boolean return value. True indicates that the receiver requires an
|
||
|
|
* asynchronous notification.
|
||
|
|
*
|
||
|
|
* After dequeuing requests or responses (before sleeping the connection):
|
||
|
|
*
|
||
|
|
* Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
|
||
|
|
* The second argument is a boolean return value. True indicates that there
|
||
|
|
* are pending messages on the ring (i.e., the connection should not be put
|
||
|
|
* to sleep).
|
||
|
|
*
|
||
|
|
* These macros will set the req_event/rsp_event field to trigger a
|
||
|
|
* notification on the very next message that is enqueued. If you want to
|
||
|
|
* create batches of work (i.e., only receive a notification after several
|
||
|
|
* messages have been enqueued) then you will need to create a customised
|
||
|
|
* version of the FINAL_CHECK macro in your own code, which sets the event
|
||
|
|
* field appropriately.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
|
||
|
|
RING_IDX __old = (_r)->sring->req_prod; \
|
||
|
|
RING_IDX __new = (_r)->req_prod_pvt; \
|
||
|
|
virt_wmb(); /* back sees requests /before/ updated producer index */ \
|
||
|
|
(_r)->sring->req_prod = __new; \
|
||
|
|
virt_mb(); /* back sees new requests /before/ we check req_event */ \
|
||
|
|
(_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
|
||
|
|
(RING_IDX)(__new - __old)); \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
|
||
|
|
RING_IDX __old = (_r)->sring->rsp_prod; \
|
||
|
|
RING_IDX __new = (_r)->rsp_prod_pvt; \
|
||
|
|
virt_wmb(); /* front sees responses /before/ updated producer index */ \
|
||
|
|
(_r)->sring->rsp_prod = __new; \
|
||
|
|
virt_mb(); /* front sees new responses /before/ we check rsp_event */ \
|
||
|
|
(_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
|
||
|
|
(RING_IDX)(__new - __old)); \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
|
||
|
|
(_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
|
||
|
|
if (_work_to_do) break; \
|
||
|
|
(_r)->sring->req_event = (_r)->req_cons + 1; \
|
||
|
|
virt_mb(); \
|
||
|
|
(_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
|
||
|
|
(_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
|
||
|
|
if (_work_to_do) break; \
|
||
|
|
(_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
|
||
|
|
virt_mb(); \
|
||
|
|
(_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
|
||
|
|
} while (0)
|
||
|
|
|
||
|
|
#endif /* __XEN_PUBLIC_IO_RING_H__ */
|