/* Virtio ring implementation.
*
* Copyright 2007 Rusty Russell IBM Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/virtio.h>
#include <linux/virtio_ring.h>
#include <linux/device.h>
#ifdef DEBUG
/* For development, we want to crash whenever the ring is screwed. */
#define BAD_RING(vq, fmt...) \
do { dev_err(&vq->vq.vdev->dev, fmt); BUG(); } while(0)
#define START_USE(vq) \
do { if ((vq)->in_use) panic("in_use = %i\n", (vq)->in_use); (vq)->in_use = __LINE__; mb(); } while(0)
#define END_USE(vq) \
do { BUG_ON(!(vq)->in_use); (vq)->in_use = 0; mb(); } while(0)
#else
#define BAD_RING(vq, fmt...) \
do { dev_err(&vq->vq.vdev->dev, fmt); (vq)->broken = true; } while(0)
#define START_USE(vq)
#define END_USE(vq)
#endif
struct vring_virtqueue
{
struct virtqueue vq;
/* Actual memory layout for this queue */
struct vring vring;
/* Other side has made a mess, don't try any more. */
bool broken;
/* Number of free buffers */
unsigned int num_free;
/* Head of free buffer list. */
unsigned int free_head;
/* Number we've added since last sync. */
unsigned int num_added;
/* Last used index we've seen. */
u16 last_used_idx;
/* How to notify other side. FIXME: commonalize hcalls! */
void (*notify)(struct virtqueue *vq);
#ifdef DEBUG
/* They're supposed to lock for us. */
unsigned int in_use;
#endif
/* Tokens for callbacks. */
void *data[];
};
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
static int vring_add_buf(struct virtqueue *_vq,
struct scatterlist sg[],
unsigned int out,
unsigned int in,
void *data)
{
struct vring_virtqueue *vq = to_vvq(_vq);
unsigned int i, avail, head, uninitialized_var(prev);
BUG_ON(data == NULL);
BUG_ON(out + in > vq->vring.num);
BUG_ON(out + in == 0);
START_USE(vq);
if (vq->num_free < out + in) {
pr_debug("Can't add buf len %i - avail = %i\n",
out + in, vq->num_free);
/* We notify *even if* VRING_USED_F_NO_NOTIFY is set here. */
vq->notify(&vq->vq);
END_USE(vq);
return -ENOSPC;
}
/* We're about to use some buffers from the free list. */
vq->num_free -= out + in;
head = vq->free_head;
for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
vq->vring.desc[i].addr = sg_phys(sg);
vq->vring.desc[i].len = sg->length;
prev = i;
sg++;
}
for (; in; i = vq->vring.desc[i].next, in--) {
vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
vq->vring.desc[i].addr = sg_phys(sg);
vq->vring.desc[i].len = sg->length;
prev = i;
sg++;
}
/* Last one doesn't continue. */
vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
/* Update free pointer */
vq->free_head = i;
/* Set token. */
vq->data[head] = data;
/* Put entry in available array (but don't update avail->idx until they
* do sync). FIXME: avoid modulus here? */
avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
vq->vring.avail->ring[avail] = head;
pr_debug("Added buffer head %i to %p\n", head, vq);
END_USE(vq);
return 0;
}
static void vring_kick(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
START_USE(vq);
/* Descriptors and available array need to be set before we expose the
* new available array entries. */
wmb();
vq->vring.avail->idx += vq->num_added;
vq->num_added = 0;
/* Need to update avail index before checking if we should notify */
mb();
if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
/* Prod other side to tell it about changes. */
vq->notify(&vq->vq);
END_USE(vq);
}
static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
{
unsigned int i;
/* Clear data ptr. */
vq->data[head] = NULL;
/* Put back on free list: find end */
i = head;
while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
i = vq->vring.desc[i].next;
vq->num_free++;
}
vq->vring.desc[i].next = vq->free_head;
vq->free_head = head;
/* Plus final descriptor */
vq->num_free++;
}
static inline bool more_used(const struct vring_virtqueue *vq)
{
return vq->last_used_idx != vq->vring.used->idx;
}
static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
{
struct vring_virtqueue *vq = to_vvq(_vq);
void *ret;
unsigned int i;
START_USE(vq);
if (!more_used(vq)) {
pr_debug("No more buffers in queue\n");
END_USE(vq);
return NULL;
}
i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
if (unlikely(i >= vq->vring.num)) {
BAD_RING(vq, "id %u out of range\n", i);
return NULL;
}
if (unlikely(!vq->data[i])) {
BAD_RING(vq, "id %u is not a head!\n", i);
return NULL;
}
/* detach_buf clears data, so grab it now. */
ret = vq->data[i];
detach_buf(vq, i);
vq->last_used_idx++;
END_USE(vq);
return ret;
}
static void vring_disable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
START_USE(vq);
BUG_ON(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
END_USE(vq);
}
static bool vring_enable_cb(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
START_USE(vq);
BUG_ON(!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT));
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
mb();
if (unlikely(more_used(vq))) {
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
END_USE(vq);
return false;
}
END_USE(vq);
return true;
}
irqreturn_t vring_interrupt(int irq, void *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
if (!more_used(vq)) {
pr_debug("virtqueue interrupt with no work for %p\n", vq);
return IRQ_NONE;
}
if (unlikely(vq->broken))
return IRQ_HANDLED;
/* Other side may have missed us turning off the interrupt,
* but we should preserve disable semantic for virtio users. */
if (unlikely(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
pr_debug("virtqueue interrupt after disable for %p\n", vq);
return IRQ_HANDLED;
}
pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
if (vq->vq.callback)
vq->vq.callback(&vq->vq);
return IRQ_HANDLED;
}
static struct virtqueue_ops vring_vq_ops = {
.add_buf = vring_add_buf,
.get_buf = vring_get_buf,
.kick = vring_kick,
.disable_cb = vring_disable_cb,
.enable_cb = vring_enable_cb,
};
struct virtqueue *vring_new_virtqueue(unsigned int num,
struct virtio_device *vdev,
void *pages,
void (*notify)(struct virtqueue *),
void (*callback)(struct virtqueue *))
{
struct vring_virtqueue *vq;
unsigned int i;
/* We assume num is a power of 2. */
if (num & (num - 1)) {
dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
return NULL;
}
vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
if (!vq)
return NULL;
vring_init(&vq->vring, num, pages, PAGE_SIZE);
vq->vq.callback = callback;
vq->vq.vdev = vdev;
vq->vq.vq_ops = &vring_vq_ops;
vq->notify = notify;
vq->broken = false;
vq->last_used_idx = 0;
vq->num_added = 0;
#ifdef DEBUG
vq->in_use = false;
#endif
/* No callback? Tell other side not to bother us. */
if (!callback)
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
/* Put everything in free lists. */
vq->num_free = num;
vq->free_head = 0;
for (i = 0; i < num-1; i++)
vq->vring.desc[i].next = i+1;
return &vq->vq;
}
void vring_del_virtqueue(struct virtqueue *vq)
{
kfree(to_vvq(vq));
}
