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|
/* 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/virtio_config.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/hrtimer.h>
/* virtio guest is communicating with a virtual "device" that actually runs on
* a host processor. Memory barriers are used to control SMP effects. */
#ifdef CONFIG_SMP
/* Where possible, use SMP barriers which are more lightweight than mandatory
* barriers, because mandatory barriers control MMIO effects on accesses
* through relaxed memory I/O windows (which virtio-pci does not use). */
#define virtio_mb(vq) \
do { if ((vq)->weak_barriers) smp_mb(); else mb(); } while(0)
#define virtio_rmb(vq) \
do { if ((vq)->weak_barriers) smp_rmb(); else rmb(); } while(0)
#define virtio_wmb(vq) \
do { if ((vq)->weak_barriers) smp_wmb(); else wmb(); } while(0)
#else
/* We must force memory ordering even if guest is UP since host could be
* running on another CPU, but SMP barriers are defined to barrier() in that
* configuration. So fall back to mandatory barriers instead. */
#define virtio_mb(vq) mb()
#define virtio_rmb(vq) rmb()
#define virtio_wmb(vq) wmb()
#endif
#ifdef DEBUG
/* For development, we want to crash whenever the ring is screwed. */
#define BAD_RING(_vq, fmt, args...) \
do { \
dev_err(&(_vq)->vq.vdev->dev, \
"%s:"fmt, (_vq)->vq.name, ##args); \
BUG(); \
} while (0)
/* Caller is supposed to guarantee no reentry. */
#define START_USE(_vq) \
do { \
if ((_vq)->in_use) \
panic("%s:in_use = %i\n", \
(_vq)->vq.name, (_vq)->in_use); \
(_vq)->in_use = __LINE__; \
} while (0)
#define END_USE(_vq) \
do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
#else
#define BAD_RING(_vq, fmt, args...) \
do { \
dev_err(&_vq->vq.vdev->dev, \
"%s:"fmt, (_vq)->vq.name, ##args); \
(_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;
/* Can we use weak barriers? */
bool weak_barriers;
/* Other side has made a mess, don't try any more. */
bool broken;
/* Host supports indirect buffers */
bool indirect;
/* Host publishes avail event idx */
bool event;
/* 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;
/* Figure out if their kicks are too delayed. */
bool last_add_time_valid;
ktime_t last_add_time;
#endif
/* Tokens for callbacks. */
void *data[];
};
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
/* Set up an indirect table of descriptors and add it to the queue. */
static int vring_add_indirect(struct vring_virtqueue *vq,
struct scatterlist sg[],
unsigned int out,
unsigned int in,
gfp_t gfp)
{
struct vring_desc *desc;
unsigned head;
int i;
/*
* We require lowmem mappings for the descriptors because
* otherwise virt_to_phys will give us bogus addresses in the
* virtqueue.
*/
gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH);
desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
if (!desc)
return -ENOMEM;
/* Transfer entries from the sg list into the indirect page */
for (i = 0; i < out; i++) {
desc[i].flags = VRING_DESC_F_NEXT;
desc[i].addr = sg_phys(sg);
desc[i].len = sg->length;
desc[i].next = i+1;
sg++;
}
for (; i < (out + in); i++) {
desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
desc[i].addr = sg_phys(sg);
desc[i].len = sg->length;
desc[i].next = i+1;
sg++;
}
/* Last one doesn't continue. */
desc[i-1].flags &= ~VRING_DESC_F_NEXT;
desc[i-1].next = 0;
/* We're about to use a buffer */
vq->vq.num_free--;
/* Use a single buffer which doesn't continue */
head = vq->free_head;
vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
vq->vring.desc[head].addr = virt_to_phys(desc);
vq->vring.desc[head].len = i * sizeof(struct vring_desc);
/* Update free pointer */
vq->free_head = vq->vring.desc[head].next;
return head;
}
/**
* virtqueue_add_buf - expose buffer to other end
* @vq: the struct virtqueue we're talking about.
* @sg: the description of the buffer(s).
* @out_num: the number of sg readable by other side
* @in_num: the number of sg which are writable (after readable ones)
* @data: the token identifying the buffer.
* @gfp: how to do memory allocations (if necessary).
*
* Caller must ensure we don't call this with other virtqueue operations
* at the same time (except where noted).
*
* Returns zero or a negative error (ie. ENOSPC, ENOMEM).
*/
int virtqueue_add_buf(struct virtqueue *_vq,
struct scatterlist sg[],
unsigned int out,
unsigned int in,
void *data,
gfp_t gfp)
{
struct vring_virtqueue *vq = to_vvq(_vq);
unsigned int i, avail, uninitialized_var(prev);
int head;
START_USE(vq);
BUG_ON(data == NULL);
#ifdef DEBUG
{
ktime_t now = ktime_get();
/* No kick or get, with .1 second between? Warn. */
if (vq->last_add_time_valid)
WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
> 100);
vq->last_add_time = now;
vq->last_add_time_valid = true;
}
#endif
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && (out + in) > 1 && vq->vq.num_free) {
head = vring_add_indirect(vq, sg, out, in, gfp);
if (likely(head >= 0))
goto add_head;
}
BUG_ON(out + in > vq->vring.num);
BUG_ON(out + in == 0);
if (vq->vq.num_free < out + in) {
pr_debug("Can't add buf len %i - avail = %i\n",
out + in, vq->vq.num_free);
/* FIXME: for historical reasons, we force a notify here if
* there are outgoing parts to the buffer. Presumably the
* host should service the ring ASAP. */
if (out)
vq->notify(&vq->vq);
END_USE(vq);
return -ENOSPC;
}
/* We're about to use some buffers from the free list. */
vq->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<
|