330 lines
7.0 KiB
C
330 lines
7.0 KiB
C
/*
|
|
* Copyright (C) 2016 Red Hat, Inc.
|
|
* Author: Michael S. Tsirkin <mst@redhat.com>
|
|
* This work is licensed under the terms of the GNU GPL, version 2.
|
|
*
|
|
* Partial implementation of virtio 0.9. event index is used for signalling,
|
|
* unconditionally. Design roughly follows linux kernel implementation in order
|
|
* to be able to judge its performance.
|
|
*/
|
|
#define _GNU_SOURCE
|
|
#include "main.h"
|
|
#include <stdlib.h>
|
|
#include <stdio.h>
|
|
#include <assert.h>
|
|
#include <string.h>
|
|
#include <linux/virtio_ring.h>
|
|
|
|
struct data {
|
|
void *data;
|
|
} *data;
|
|
|
|
struct vring ring;
|
|
|
|
/* enabling the below activates experimental ring polling code
|
|
* (which skips index reads on consumer in favor of looking at
|
|
* high bits of ring id ^ 0x8000).
|
|
*/
|
|
/* #ifdef RING_POLL */
|
|
/* enabling the below activates experimental in-order code
|
|
* (which skips ring updates and reads and writes len in descriptor).
|
|
*/
|
|
/* #ifdef INORDER */
|
|
|
|
#if defined(RING_POLL) && defined(INORDER)
|
|
#error "RING_POLL and INORDER are mutually exclusive"
|
|
#endif
|
|
|
|
/* how much padding is needed to avoid false cache sharing */
|
|
#define HOST_GUEST_PADDING 0x80
|
|
|
|
struct guest {
|
|
unsigned short avail_idx;
|
|
unsigned short last_used_idx;
|
|
unsigned short num_free;
|
|
unsigned short kicked_avail_idx;
|
|
#ifndef INORDER
|
|
unsigned short free_head;
|
|
#else
|
|
unsigned short reserved_free_head;
|
|
#endif
|
|
unsigned char reserved[HOST_GUEST_PADDING - 10];
|
|
} guest;
|
|
|
|
struct host {
|
|
/* we do not need to track last avail index
|
|
* unless we have more than one in flight.
|
|
*/
|
|
unsigned short used_idx;
|
|
unsigned short called_used_idx;
|
|
unsigned char reserved[HOST_GUEST_PADDING - 4];
|
|
} host;
|
|
|
|
/* implemented by ring */
|
|
void alloc_ring(void)
|
|
{
|
|
int ret;
|
|
int i;
|
|
void *p;
|
|
|
|
ret = posix_memalign(&p, 0x1000, vring_size(ring_size, 0x1000));
|
|
if (ret) {
|
|
perror("Unable to allocate ring buffer.\n");
|
|
exit(3);
|
|
}
|
|
memset(p, 0, vring_size(ring_size, 0x1000));
|
|
vring_init(&ring, ring_size, p, 0x1000);
|
|
|
|
guest.avail_idx = 0;
|
|
guest.kicked_avail_idx = -1;
|
|
guest.last_used_idx = 0;
|
|
#ifndef INORDER
|
|
/* Put everything in free lists. */
|
|
guest.free_head = 0;
|
|
#endif
|
|
for (i = 0; i < ring_size - 1; i++)
|
|
ring.desc[i].next = i + 1;
|
|
host.used_idx = 0;
|
|
host.called_used_idx = -1;
|
|
guest.num_free = ring_size;
|
|
data = malloc(ring_size * sizeof *data);
|
|
if (!data) {
|
|
perror("Unable to allocate data buffer.\n");
|
|
exit(3);
|
|
}
|
|
memset(data, 0, ring_size * sizeof *data);
|
|
}
|
|
|
|
/* guest side */
|
|
int add_inbuf(unsigned len, void *buf, void *datap)
|
|
{
|
|
unsigned head;
|
|
#ifndef INORDER
|
|
unsigned avail;
|
|
#endif
|
|
struct vring_desc *desc;
|
|
|
|
if (!guest.num_free)
|
|
return -1;
|
|
|
|
#ifdef INORDER
|
|
head = (ring_size - 1) & (guest.avail_idx++);
|
|
#else
|
|
head = guest.free_head;
|
|
#endif
|
|
guest.num_free--;
|
|
|
|
desc = ring.desc;
|
|
desc[head].flags = VRING_DESC_F_NEXT;
|
|
desc[head].addr = (unsigned long)(void *)buf;
|
|
desc[head].len = len;
|
|
/* We do it like this to simulate the way
|
|
* we'd have to flip it if we had multiple
|
|
* descriptors.
|
|
*/
|
|
desc[head].flags &= ~VRING_DESC_F_NEXT;
|
|
#ifndef INORDER
|
|
guest.free_head = desc[head].next;
|
|
#endif
|
|
|
|
data[head].data = datap;
|
|
|
|
#ifdef RING_POLL
|
|
/* Barrier A (for pairing) */
|
|
smp_release();
|
|
avail = guest.avail_idx++;
|
|
ring.avail->ring[avail & (ring_size - 1)] =
|
|
(head | (avail & ~(ring_size - 1))) ^ 0x8000;
|
|
#else
|
|
#ifndef INORDER
|
|
/* Barrier A (for pairing) */
|
|
smp_release();
|
|
avail = (ring_size - 1) & (guest.avail_idx++);
|
|
ring.avail->ring[avail] = head;
|
|
#endif
|
|
/* Barrier A (for pairing) */
|
|
smp_release();
|
|
#endif
|
|
ring.avail->idx = guest.avail_idx;
|
|
return 0;
|
|
}
|
|
|
|
void *get_buf(unsigned *lenp, void **bufp)
|
|
{
|
|
unsigned head;
|
|
unsigned index;
|
|
void *datap;
|
|
|
|
#ifdef RING_POLL
|
|
head = (ring_size - 1) & guest.last_used_idx;
|
|
index = ring.used->ring[head].id;
|
|
if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))
|
|
return NULL;
|
|
/* Barrier B (for pairing) */
|
|
smp_acquire();
|
|
index &= ring_size - 1;
|
|
#else
|
|
if (ring.used->idx == guest.last_used_idx)
|
|
return NULL;
|
|
/* Barrier B (for pairing) */
|
|
smp_acquire();
|
|
#ifdef INORDER
|
|
head = (ring_size - 1) & guest.last_used_idx;
|
|
index = head;
|
|
#else
|
|
head = (ring_size - 1) & guest.last_used_idx;
|
|
index = ring.used->ring[head].id;
|
|
#endif
|
|
|
|
#endif
|
|
#ifdef INORDER
|
|
*lenp = ring.desc[index].len;
|
|
#else
|
|
*lenp = ring.used->ring[head].len;
|
|
#endif
|
|
datap = data[index].data;
|
|
*bufp = (void*)(unsigned long)ring.desc[index].addr;
|
|
data[index].data = NULL;
|
|
#ifndef INORDER
|
|
ring.desc[index].next = guest.free_head;
|
|
guest.free_head = index;
|
|
#endif
|
|
guest.num_free++;
|
|
guest.last_used_idx++;
|
|
return datap;
|
|
}
|
|
|
|
bool used_empty()
|
|
{
|
|
unsigned short last_used_idx = guest.last_used_idx;
|
|
#ifdef RING_POLL
|
|
unsigned short head = last_used_idx & (ring_size - 1);
|
|
unsigned index = ring.used->ring[head].id;
|
|
|
|
return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);
|
|
#else
|
|
return ring.used->idx == last_used_idx;
|
|
#endif
|
|
}
|
|
|
|
void disable_call()
|
|
{
|
|
/* Doing nothing to disable calls might cause
|
|
* extra interrupts, but reduces the number of cache misses.
|
|
*/
|
|
}
|
|
|
|
bool enable_call()
|
|
{
|
|
vring_used_event(&ring) = guest.last_used_idx;
|
|
/* Flush call index write */
|
|
/* Barrier D (for pairing) */
|
|
smp_mb();
|
|
return used_empty();
|
|
}
|
|
|
|
void kick_available(void)
|
|
{
|
|
/* Flush in previous flags write */
|
|
/* Barrier C (for pairing) */
|
|
smp_mb();
|
|
if (!vring_need_event(vring_avail_event(&ring),
|
|
guest.avail_idx,
|
|
guest.kicked_avail_idx))
|
|
return;
|
|
|
|
guest.kicked_avail_idx = guest.avail_idx;
|
|
kick();
|
|
}
|
|
|
|
/* host side */
|
|
void disable_kick()
|
|
{
|
|
/* Doing nothing to disable kicks might cause
|
|
* extra interrupts, but reduces the number of cache misses.
|
|
*/
|
|
}
|
|
|
|
bool enable_kick()
|
|
{
|
|
vring_avail_event(&ring) = host.used_idx;
|
|
/* Barrier C (for pairing) */
|
|
smp_mb();
|
|
return avail_empty();
|
|
}
|
|
|
|
bool avail_empty()
|
|
{
|
|
unsigned head = host.used_idx;
|
|
#ifdef RING_POLL
|
|
unsigned index = ring.avail->ring[head & (ring_size - 1)];
|
|
|
|
return ((index ^ head ^ 0x8000) & ~(ring_size - 1));
|
|
#else
|
|
return head == ring.avail->idx;
|
|
#endif
|
|
}
|
|
|
|
bool use_buf(unsigned *lenp, void **bufp)
|
|
{
|
|
unsigned used_idx = host.used_idx;
|
|
struct vring_desc *desc;
|
|
unsigned head;
|
|
|
|
#ifdef RING_POLL
|
|
head = ring.avail->ring[used_idx & (ring_size - 1)];
|
|
if ((used_idx ^ head ^ 0x8000) & ~(ring_size - 1))
|
|
return false;
|
|
/* Barrier A (for pairing) */
|
|
smp_acquire();
|
|
|
|
used_idx &= ring_size - 1;
|
|
desc = &ring.desc[head & (ring_size - 1)];
|
|
#else
|
|
if (used_idx == ring.avail->idx)
|
|
return false;
|
|
|
|
/* Barrier A (for pairing) */
|
|
smp_acquire();
|
|
|
|
used_idx &= ring_size - 1;
|
|
#ifdef INORDER
|
|
head = used_idx;
|
|
#else
|
|
head = ring.avail->ring[used_idx];
|
|
#endif
|
|
desc = &ring.desc[head];
|
|
#endif
|
|
|
|
*lenp = desc->len;
|
|
*bufp = (void *)(unsigned long)desc->addr;
|
|
|
|
#ifdef INORDER
|
|
desc->len = desc->len - 1;
|
|
#else
|
|
/* now update used ring */
|
|
ring.used->ring[used_idx].id = head;
|
|
ring.used->ring[used_idx].len = desc->len - 1;
|
|
#endif
|
|
/* Barrier B (for pairing) */
|
|
smp_release();
|
|
host.used_idx++;
|
|
ring.used->idx = host.used_idx;
|
|
|
|
return true;
|
|
}
|
|
|
|
void call_used(void)
|
|
{
|
|
/* Flush in previous flags write */
|
|
/* Barrier D (for pairing) */
|
|
smp_mb();
|
|
if (!vring_need_event(vring_used_event(&ring),
|
|
host.used_idx,
|
|
host.called_used_idx))
|
|
return;
|
|
|
|
host.called_used_idx = host.used_idx;
|
|
call();
|
|
}
|