/* 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> RING_IDX; /* Round a 32-bit unsigned constant down to the nearest power of two. */ #define __RD2(_x) … #define __RD4(_x) … #define __RD8(_x) … #define __RD16(_x) … #define __RD32(_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) … /* * The same for passing in an actual pointer instead of a name tag. */ #define __RING_SIZE(_s, _sz) … /* * 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 ring; * XEN_FRONT_RING_INIT(&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) … /* Initialising empty rings */ #define SHARED_RING_INIT(_s) … #define FRONT_RING_ATTACH(_r, _s, _i, __size) … #define FRONT_RING_INIT(_r, _s, __size) … #define XEN_FRONT_RING_INIT(r, s, size) … #define BACK_RING_ATTACH(_r, _s, _i, __size) … #define BACK_RING_INIT(_r, _s, __size) … /* How big is this ring? */ #define RING_SIZE(_r) … /* Number of free requests (for use on front side only). */ #define RING_FREE_REQUESTS(_r) … /* Test if there is an empty slot available on the front ring. * (This is only meaningful from the front. ) */ #define RING_FULL(_r) … /* Test if there are outstanding messages to be processed on a ring. */ #define XEN_RING_NR_UNCONSUMED_RESPONSES(_r) … #define XEN_RING_NR_UNCONSUMED_REQUESTS(_r) … #define RING_HAS_UNCONSUMED_RESPONSES(_r) … #define RING_HAS_UNCONSUMED_REQUESTS(_r) … /* Direct access to individual ring elements, by index. */ #define RING_GET_REQUEST(_r, _idx) … #define RING_GET_RESPONSE(_r, _idx) … /* * 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) … #define RING_COPY_REQUEST(r, idx, req) … #define RING_COPY_RESPONSE(r, idx, rsp) … /* Loop termination condition: Would the specified index overflow the ring? */ #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) … /* Ill-behaved frontend determination: Can there be this many requests? */ #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) … /* Ill-behaved backend determination: Can there be this many responses? */ #define RING_RESPONSE_PROD_OVERFLOW(_r, _prod) … #define RING_PUSH_REQUESTS(_r) … #define RING_PUSH_RESPONSES(_r) … /* * 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) … #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) … #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) … #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) … /* * 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 … #endif #define XEN_FLEX_RING_SIZE(order) … #define DEFINE_XEN_FLEX_RING(name) … #define DEFINE_XEN_FLEX_RING_AND_INTF(name) … #endif /* __XEN_PUBLIC_IO_RING_H__ */
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