| /* SPDX-License-Identifier: MIT */ |
| /****************************************************************************** |
| * 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__ |
| |
| /* |
| * When #include'ing this header, you need to provide the following |
| * declaration upfront: |
| * - standard integers types (uint8_t, uint16_t, etc) |
| * They are provided by stdint.h of the standard headers. |
| * |
| * In addition, if you intend to use the FLEX macros, you also need to |
| * provide the following, before invoking the FLEX macros: |
| * - size_t |
| * - memcpy |
| * - grant_ref_t |
| * These declarations are provided by string.h of the standard headers, |
| * and grant_table.h from the Xen public headers. |
| */ |
| |
| #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 request_t, and response_t already defined. |
| * |
| * In a header where you want the ring datatype declared, you then do: |
| * |
| * DEFINE_RING_TYPES(mytag, request_t, response_t); |
| * |
| * These expand out to give you a set of types, as you can see below. |
| * The most important of these are: |
| * |
| * mytag_sring_t - The shared ring. |
| * mytag_front_ring_t - The 'front' half of the ring. |
| * mytag_back_ring_t - 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: |
| * |
| * mytag_front_ring_t front_ring; |
| * SHARED_RING_INIT((mytag_sring_t *)shared_page); |
| * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); |
| * |
| * Initializing the back follows similarly (note that only the front |
| * initializes the shared ring): |
| * |
| * mytag_back_ring_t back_ring; |
| * BACK_RING_INIT(&back_ring, (mytag_sring_t *)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; \ |
| (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \ |
| } while(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 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) |
| |
| #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) |
| |
| /* 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)) |
| |
| #define RING_GET_RESPONSE(_r, _idx) \ |
| (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) |
| |
| /* |
| * Get a local copy of a request/response. |
| * |
| * Use this in preference to RING_GET_{REQUEST,RESPONSE}() 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 dest is a struct which consists of only bitfields. |
| */ |
| #define RING_COPY_(type, r, idx, dest) do { \ |
| /* Use volatile to force the copy into dest. */ \ |
| *(dest) = *(volatile typeof(dest))RING_GET_##type(r, idx); \ |
| } while (0) |
| |
| #define RING_COPY_REQUEST(r, idx, req) RING_COPY_(REQUEST, r, idx, req) |
| #define RING_COPY_RESPONSE(r, idx, rsp) RING_COPY_(RESPONSE, r, idx, 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)) |
| |
| /* Ill-behaved backend determination: Can there be this many responses? */ |
| #define RING_RESPONSE_PROD_OVERFLOW(_r, _prod) \ |
| (((_prod) - (_r)->rsp_cons) > 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 resps /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 resps /before/ updated producer index */ \ |
| (_r)->sring->rsp_prod = __new; \ |
| virt_mb(); /* front sees new resps /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__ */ |
