| /* SPDX-License-Identifier: GPL-2.0 */ | |
| /****************************************************************************** | |
| * 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__ | |
| #include <xen/interface/grant_table.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) | |
| /* | |
| * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and | |
| * functions to check if there is data on the ring, and to read and | |
| * write to them. | |
| * | |
| * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but | |
| * does not define the indexes page. As different protocols can have | |
| * extensions to the basic format, this macro allow them to define their | |
| * own struct. | |
| * | |
| * XEN_FLEX_RING_SIZE | |
| * Convenience macro to calculate the size of one of the two rings | |
| * from the overall order. | |
| * | |
| * $NAME_mask | |
| * Function to apply the size mask to an index, to reduce the index | |
| * within the range [0-size]. | |
| * | |
| * $NAME_read_packet | |
| * Function to read data from the ring. The amount of data to read is | |
| * specified by the "size" argument. | |
| * | |
| * $NAME_write_packet | |
| * Function to write data to the ring. The amount of data to write is | |
| * specified by the "size" argument. | |
| * | |
| * $NAME_get_ring_ptr | |
| * Convenience function that returns a pointer to read/write to the | |
| * ring at the right location. | |
| * | |
| * $NAME_data_intf | |
| * Indexes page, shared between frontend and backend. It also | |
| * contains the array of grant refs. | |
| * | |
| * $NAME_queued | |
| * Function to calculate how many bytes are currently on the ring, | |
| * ready to be read. It can also be used to calculate how much free | |
| * space is currently on the ring (XEN_FLEX_RING_SIZE() - | |
| * $NAME_queued()). | |
| */ | |
| #ifndef XEN_PAGE_SHIFT | |
| /* The PAGE_SIZE for ring protocols and hypercall interfaces is always | |
| * 4K, regardless of the architecture, and page granularity chosen by | |
| * operating systems. | |
| */ | |
| #define XEN_PAGE_SHIFT 12 | |
| #endif | |
| #define XEN_FLEX_RING_SIZE(order) \ | |
| (1UL << ((order) + XEN_PAGE_SHIFT - 1)) | |
| #define DEFINE_XEN_FLEX_RING(name) \ | |
| static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \ | |
| { \ | |
| return idx & (ring_size - 1); \ | |
| } \ | |
| \ | |
| static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \ | |
| RING_IDX idx, \ | |
| RING_IDX ring_size) \ | |
| { \ | |
| return buf + name##_mask(idx, ring_size); \ | |
| } \ | |
| \ | |
| static inline void name##_read_packet(void *opaque, \ | |
| const unsigned char *buf, \ | |
| size_t size, \ | |
| RING_IDX masked_prod, \ | |
| RING_IDX *masked_cons, \ | |
| RING_IDX ring_size) \ | |
| { \ | |
| if (*masked_cons < masked_prod || \ | |
| size <= ring_size - *masked_cons) { \ | |
| memcpy(opaque, buf + *masked_cons, size); \ | |
| } else { \ | |
| memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \ | |
| memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \ | |
| size - (ring_size - *masked_cons)); \ | |
| } \ | |
| *masked_cons = name##_mask(*masked_cons + size, ring_size); \ | |
| } \ | |
| \ | |
| static inline void name##_write_packet(unsigned char *buf, \ | |
| const void *opaque, \ | |
| size_t size, \ | |
| RING_IDX *masked_prod, \ | |
| RING_IDX masked_cons, \ | |
| RING_IDX ring_size) \ | |
| { \ | |
| if (*masked_prod < masked_cons || \ | |
| size <= ring_size - *masked_prod) { \ | |
| memcpy(buf + *masked_prod, opaque, size); \ | |
| } else { \ | |
| memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \ | |
| memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \ | |
| size - (ring_size - *masked_prod)); \ | |
| } \ | |
| *masked_prod = name##_mask(*masked_prod + size, ring_size); \ | |
| } \ | |
| \ | |
| static inline RING_IDX name##_queued(RING_IDX prod, \ | |
| RING_IDX cons, \ | |
| RING_IDX ring_size) \ | |
| { \ | |
| RING_IDX size; \ | |
| \ | |
| if (prod == cons) \ | |
| return 0; \ | |
| \ | |
| prod = name##_mask(prod, ring_size); \ | |
| cons = name##_mask(cons, ring_size); \ | |
| \ | |
| if (prod == cons) \ | |
| return ring_size; \ | |
| \ | |
| if (prod > cons) \ | |
| size = prod - cons; \ | |
| else \ | |
| size = ring_size - (cons - prod); \ | |
| return size; \ | |
| } \ | |
| \ | |
| struct name##_data { \ | |
| unsigned char *in; /* half of the allocation */ \ | |
| unsigned char *out; /* half of the allocation */ \ | |
| } | |
| #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \ | |
| struct name##_data_intf { \ | |
| RING_IDX in_cons, in_prod; \ | |
| \ | |
| uint8_t pad1[56]; \ | |
| \ | |
| RING_IDX out_cons, out_prod; \ | |
| \ | |
| uint8_t pad2[56]; \ | |
| \ | |
| RING_IDX ring_order; \ | |
| grant_ref_t ref[]; \ | |
| }; \ | |
| DEFINE_XEN_FLEX_RING(name) | |
| #endif /* __XEN_PUBLIC_IO_RING_H__ */ |