^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) // SPDX-License-Identifier: GPL-2.0-only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) /*
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) * Copyright (C) 2016 Red Hat, Inc.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4) * Author: Michael S. Tsirkin <mst@redhat.com>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) *
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) * Simple descriptor-based ring. virtio 0.9 compatible event index is used for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) * signalling, unconditionally.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) #define _GNU_SOURCE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) #include "main.h"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) #include <stdlib.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) #include <stdio.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) #include <string.h>
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) /* Next - Where next entry will be written.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) * Prev - "Next" value when event triggered previously.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) * Event - Peer requested event after writing this entry.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) static inline bool need_event(unsigned short event,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) unsigned short next,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) unsigned short prev)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23) return (unsigned short)(next - event - 1) < (unsigned short)(next - prev);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) /* Design:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) * Guest adds descriptors with unique index values and DESC_HW in flags.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) * Host overwrites used descriptors with correct len, index, and DESC_HW clear.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) * Flags are always set last.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) #define DESC_HW 0x1
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) struct desc {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) unsigned short flags;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) unsigned short index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) unsigned len;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) unsigned long long addr;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) /* how much padding is needed to avoid false cache sharing */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) #define HOST_GUEST_PADDING 0x80
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) /* Mostly read */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44) struct event {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) unsigned short kick_index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46) unsigned char reserved0[HOST_GUEST_PADDING - 2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) unsigned short call_index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48) unsigned char reserved1[HOST_GUEST_PADDING - 2];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) struct data {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52) void *buf; /* descriptor is writeable, we can't get buf from there */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) void *data;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) } *data;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56) struct desc *ring;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) struct event *event;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) struct guest {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60) unsigned avail_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) unsigned last_used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) unsigned num_free;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) unsigned kicked_avail_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) unsigned char reserved[HOST_GUEST_PADDING - 12];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) } guest;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) struct host {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68) /* we do not need to track last avail index
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) * unless we have more than one in flight.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) unsigned used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) unsigned called_used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) unsigned char reserved[HOST_GUEST_PADDING - 4];
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) } host;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) /* implemented by ring */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) void alloc_ring(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) int ret;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80) int i;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82) ret = posix_memalign((void **)&ring, 0x1000, ring_size * sizeof *ring);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) if (ret) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84) perror("Unable to allocate ring buffer.\n");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) exit(3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) event = calloc(1, sizeof(*event));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88) if (!event) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) perror("Unable to allocate event buffer.\n");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90) exit(3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92) guest.avail_idx = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) guest.kicked_avail_idx = -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94) guest.last_used_idx = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) host.used_idx = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96) host.called_used_idx = -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) for (i = 0; i < ring_size; ++i) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98) struct desc desc = {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) .index = i,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) };
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) ring[i] = desc;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) guest.num_free = ring_size;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) data = calloc(ring_size, sizeof(*data));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) if (!data) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) perror("Unable to allocate data buffer.\n");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) exit(3);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) /* guest side */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) int add_inbuf(unsigned len, void *buf, void *datap)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) unsigned head, index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) if (!guest.num_free)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) return -1;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) guest.num_free--;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) head = (ring_size - 1) & (guest.avail_idx++);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) /* Start with a write. On MESI architectures this helps
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) * avoid a shared state with consumer that is polling this descriptor.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) ring[head].addr = (unsigned long)(void*)buf;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) ring[head].len = len;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) /* read below might bypass write above. That is OK because it's just an
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) * optimization. If this happens, we will get the cache line in a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) * shared state which is unfortunate, but probably not worth it to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) * add an explicit full barrier to avoid this.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) barrier();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) index = ring[head].index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) data[index].buf = buf;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) data[index].data = datap;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) /* Barrier A (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) smp_release();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) ring[head].flags = DESC_HW;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) return 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) void *get_buf(unsigned *lenp, void **bufp)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) unsigned head = (ring_size - 1) & guest.last_used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) unsigned index;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) void *datap;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) if (ring[head].flags & DESC_HW)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) return NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) /* Barrier B (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) smp_acquire();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) *lenp = ring[head].len;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) index = ring[head].index & (ring_size - 1);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) datap = data[index].data;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) *bufp = data[index].buf;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) data[index].buf = NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) data[index].data = NULL;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) guest.num_free++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) guest.last_used_idx++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) return datap;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) bool used_empty()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) unsigned head = (ring_size - 1) & guest.last_used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) return (ring[head].flags & DESC_HW);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) void disable_call()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) /* Doing nothing to disable calls might cause
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) * extra interrupts, but reduces the number of cache misses.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) bool enable_call()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) event->call_index = guest.last_used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) /* Flush call index write */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) /* Barrier D (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) smp_mb();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) return used_empty();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) void kick_available(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) bool need;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) /* Flush in previous flags write */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) /* Barrier C (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) smp_mb();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) need = need_event(event->kick_index,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) guest.avail_idx,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) guest.kicked_avail_idx);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) guest.kicked_avail_idx = guest.avail_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) if (need)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) kick();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) /* host side */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) void disable_kick()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) /* Doing nothing to disable kicks might cause
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) * extra interrupts, but reduces the number of cache misses.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) bool enable_kick()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) event->kick_index = host.used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) /* Barrier C (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) smp_mb();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) return avail_empty();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) bool avail_empty()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221) unsigned head = (ring_size - 1) & host.used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) return !(ring[head].flags & DESC_HW);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) bool use_buf(unsigned *lenp, void **bufp)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228) unsigned head = (ring_size - 1) & host.used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230) if (!(ring[head].flags & DESC_HW))
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) return false;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) /* make sure length read below is not speculated */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234) /* Barrier A (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) smp_acquire();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237) /* simple in-order completion: we don't need
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238) * to touch index at all. This also means we
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) * can just modify the descriptor in-place.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241) ring[head].len--;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242) /* Make sure len is valid before flags.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243) * Note: alternative is to write len and flags in one access -
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244) * possible on 64 bit architectures but wmb is free on Intel anyway
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) * so I have no way to test whether it's a gain.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247) /* Barrier B (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248) smp_release();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) ring[head].flags = 0;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250) host.used_idx++;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251) return true;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254) void call_used(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256) bool need;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258) /* Flush in previous flags write */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) /* Barrier D (for pairing) */
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260) smp_mb();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262) need = need_event(event->call_index,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) host.used_idx,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264) host.called_used_idx);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) host.called_used_idx = host.used_idx;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) if (need)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 269) call();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 270) }
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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