1 // SPDX-License-Identifier: GPL-2.0-only
6  * Partial implementation of virtio 0.9. event index is used for signalling,
25  * (which skips index reads on consumer in favor of looking at
26  * high bits of ring id ^ 0x8000).
29 /* enabling the below activates experimental in-order code
41 struct guest {  struct
51 	unsigned char reserved[HOST_GUEST_PADDING - 10];
52 } guest;  argument
55 	/* we do not need to track last avail index
60 	unsigned char reserved[HOST_GUEST_PADDING - 4];
78 	guest.avail_idx = 0;  in alloc_ring()
79 	guest.kicked_avail_idx = -1;  in alloc_ring()
80 	guest.last_used_idx = 0;  in alloc_ring()
83 	guest.free_head = 0;  in alloc_ring()
85 	for (i = 0; i < ring_size - 1; i++)  in alloc_ring()
88 	host.called_used_idx = -1;  in alloc_ring()
89 	guest.num_free = ring_size;  in alloc_ring()
98 /* guest side */
107 	if (!guest.num_free)  in add_inbuf()
108 		return -1;  in add_inbuf()
111 	head = (ring_size - 1) & (guest.avail_idx++);  in add_inbuf()
113 	head = guest.free_head;  in add_inbuf()
115 	guest.num_free--;  in add_inbuf()
127 	guest.free_head = desc[head].next;  in add_inbuf()
135 	avail = guest.avail_idx++;  in add_inbuf()
136 	ring.avail->ring[avail & (ring_size - 1)] =  in add_inbuf()
137 		(head | (avail & ~(ring_size - 1))) ^ 0x8000;  in add_inbuf()
142 	avail = (ring_size - 1) & (guest.avail_idx++);  in add_inbuf()
143 	ring.avail->ring[avail] = head;  in add_inbuf()
148 	ring.avail->idx = guest.avail_idx;  in add_inbuf()
155 	unsigned index;  in get_buf()  local
159 	head = (ring_size - 1) & guest.last_used_idx;  in get_buf()
160 	index = ring.used->ring[head].id;  in get_buf()
161 	if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))  in get_buf()
165 	index &= ring_size - 1;  in get_buf()
167 	if (ring.used->idx == guest.last_used_idx)  in get_buf()
172 	head = (ring_size - 1) & guest.last_used_idx;  in get_buf()
173 	index = head;  in get_buf()
175 	head = (ring_size - 1) & guest.last_used_idx;  in get_buf()
176 	index = ring.used->ring[head].id;  in get_buf()
181 	*lenp = ring.desc[index].len;  in get_buf()
183 	*lenp = ring.used->ring[head].len;  in get_buf()
185 	datap = data[index].data;  in get_buf()
186 	*bufp = (void*)(unsigned long)ring.desc[index].addr;  in get_buf()
187 	data[index].data = NULL;  in get_buf()
189 	ring.desc[index].next = guest.free_head;  in get_buf()
190 	guest.free_head = index;  in get_buf()
192 	guest.num_free++;  in get_buf()
193 	guest.last_used_idx++;  in get_buf()
199 	unsigned short last_used_idx = guest.last_used_idx;  in used_empty()
201 	unsigned short head = last_used_idx & (ring_size - 1);  in used_empty()
202 	unsigned index = ring.used->ring[head].id;  in used_empty()  local
204 	return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);  in used_empty()
206 	return ring.used->idx == last_used_idx;  in used_empty()
219 	vring_used_event(&ring) = guest.last_used_idx;  in enable_call()
220 	/* Flush call index write */  in enable_call()
234 				guest.avail_idx,  in kick_available()
235 				guest.kicked_avail_idx);  in kick_available()
237 	guest.kicked_avail_idx = guest.avail_idx;  in kick_available()
262 	unsigned index = ring.avail->ring[head & (ring_size - 1)];  in avail_empty()  local
264 	return ((index ^ head ^ 0x8000) & ~(ring_size - 1));  in avail_empty()
266 	return head == ring.avail->idx;  in avail_empty()
277 	head = ring.avail->ring[used_idx & (ring_size - 1)];  in use_buf()
278 	if ((used_idx ^ head ^ 0x8000) & ~(ring_size - 1))  in use_buf()
283 	used_idx &= ring_size - 1;  in use_buf()
284 	desc = &ring.desc[head & (ring_size - 1)];  in use_buf()
286 	if (used_idx == ring.avail->idx)  in use_buf()
292 	used_idx &= ring_size - 1;  in use_buf()
296 	head = ring.avail->ring[used_idx];  in use_buf()
301 	*lenp = desc->len;  in use_buf()
302 	*bufp = (void *)(unsigned long)desc->addr;  in use_buf()
305 	desc->len = desc->len - 1;  in use_buf()
308 	ring.used->ring[used_idx].id = head;  in use_buf()
309 	ring.used->ring[used_idx].len = desc->len - 1;  in use_buf()
314 	ring.used->idx = host.used_idx;  in use_buf()