#include <linux/virtio_config.h>
#include <linux/device.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 does not use). */
+#define virtio_mb() smp_mb()
+#define virtio_rmb() smp_rmb()
+#define virtio_wmb() smp_wmb()
+#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() mb()
+#define virtio_rmb() rmb()
+#define virtio_wmb() wmb()
+#endif
+
#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 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("in_use = %i\n", (_vq)->in_use); \
+ panic("%s:in_use = %i\n", \
+ (_vq)->vq.name, (_vq)->in_use); \
(_vq)->in_use = __LINE__; \
- mb(); \
- } while(0)
+ } while (0)
#define END_USE(_vq) \
- do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
+ do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
#else
-#define BAD_RING(_vq, fmt...) \
- do { dev_err(&_vq->vq.vdev->dev, fmt); (_vq)->broken = true; } while(0)
+#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
/* Other side has made a mess, don't try any more. */
bool broken;
+ /* Host supports indirect buffers */
+ bool indirect;
+
/* Number of free buffers */
unsigned int num_free;
/* Head of free buffer list. */
#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)
+{
+ struct vring_desc *desc;
+ unsigned head;
+ int i;
+
+ desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
+ if (!desc)
+ return vq->vring.num;
+
+ /* 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->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;
+}
+
static int vring_add_buf(struct virtqueue *_vq,
struct scatterlist sg[],
unsigned int out,
struct vring_virtqueue *vq = to_vvq(_vq);
unsigned int i, avail, head, uninitialized_var(prev);
+ START_USE(vq);
+
BUG_ON(data == NULL);
+
+ /* 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->num_free) {
+ head = vring_add_indirect(vq, sg, out, in);
+ if (head != vq->vring.num)
+ goto add_head;
+ }
+
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);
/* Update free pointer */
vq->free_head = i;
+add_head:
/* Set token. */
vq->data[head] = data;
pr_debug("Added buffer head %i to %p\n", head, vq);
END_USE(vq);
- return 0;
+
+ /* If we're indirect, we can fit many (assuming not OOM). */
+ if (vq->indirect)
+ return vq->num_free ? vq->vring.num : 0;
+ return vq->num_free;
}
static void vring_kick(struct virtqueue *_vq)
START_USE(vq);
/* Descriptors and available array need to be set before we expose the
* new available array entries. */
- wmb();
+ virtio_wmb();
vq->vring.avail->idx += vq->num_added;
vq->num_added = 0;
/* Need to update avail index before checking if we should notify */
- mb();
+ virtio_mb();
if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
/* Prod other side to tell it about changes. */
/* Put back on free list: find end */
i = head;
+
+ /* Free the indirect table */
+ if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
+ kfree(phys_to_virt(vq->vring.desc[i].addr));
+
while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
i = vq->vring.desc[i].next;
vq->num_free++;
return NULL;
}
+ /* Only get used array entries after they have been exposed by host. */
+ virtio_rmb();
+
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;
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
- mb();
+ virtio_mb();
if (unlikely(more_used(vq))) {
END_USE(vq);
return false;
return true;
}
+static void *vring_detach_unused_buf(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ unsigned int i;
+ void *buf;
+
+ START_USE(vq);
+
+ for (i = 0; i < vq->vring.num; i++) {
+ if (!vq->data[i])
+ continue;
+ /* detach_buf clears data, so grab it now. */
+ buf = vq->data[i];
+ detach_buf(vq, i);
+ END_USE(vq);
+ return buf;
+ }
+ /* That should have freed everything. */
+ BUG_ON(vq->num_free != vq->vring.num);
+
+ END_USE(vq);
+ return NULL;
+}
+
irqreturn_t vring_interrupt(int irq, void *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
.kick = vring_kick,
.disable_cb = vring_disable_cb,
.enable_cb = vring_enable_cb,
+ .detach_unused_buf = vring_detach_unused_buf,
};
struct virtqueue *vring_new_virtqueue(unsigned int num,
struct virtio_device *vdev,
void *pages,
void (*notify)(struct virtqueue *),
- void (*callback)(struct virtqueue *))
+ void (*callback)(struct virtqueue *),
+ const char *name)
{
struct vring_virtqueue *vq;
unsigned int i;
vq->vq.callback = callback;
vq->vq.vdev = vdev;
vq->vq.vq_ops = &vring_vq_ops;
+ vq->vq.name = name;
vq->notify = notify;
vq->broken = false;
vq->last_used_idx = 0;
vq->num_added = 0;
+ list_add_tail(&vq->vq.list, &vdev->vqs);
#ifdef DEBUG
vq->in_use = false;
#endif
+ vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
+
/* No callback? Tell other side not to bother us. */
if (!callback)
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
void vring_del_virtqueue(struct virtqueue *vq)
{
+ list_del(&vq->list);
kfree(to_vvq(vq));
}
EXPORT_SYMBOL_GPL(vring_del_virtqueue);
for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
switch (i) {
+ case VIRTIO_RING_F_INDIRECT_DESC:
+ break;
default:
/* We don't understand this bit. */
clear_bit(i, vdev->features);
Code Review / linux-2.6.git / blobdiff