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Message-Id: <1360671815-2135-10-git-send-email-pbonzini@redhat.com>
Date: Tue, 12 Feb 2013 13:23:35 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Wanlong Gao <gaowanlong@...fujitsu.com>, asias@...hat.com,
mst@...hat.com, Rusty Russell <rusty@...tcorp.com.au>,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [PATCH 9/9] virtio: reimplement virtqueue_add_buf using new functions
Eliminate the code duplication between virtqueue_add_buf and
virtqueue_add_sg. That's safe to do now that no devices will
pass scatterlists with a termination marker in the middle.
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
drivers/virtio/virtio_ring.c | 159 +++---------------------------------------
1 files changed, 11 insertions(+), 148 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index b803cf7..71488c5 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -123,63 +123,6 @@ struct vring_virtqueue
#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_single - expose a single scatterlist entry to other end
* @vq: the struct virtqueue we're talking about.
@@ -234,104 +177,25 @@ EXPORT_SYMBOL_GPL(virtqueue_add_buf_single);
*
* Returns zero or a negative error (ie. ENOSPC, ENOMEM).
*/
-int virtqueue_add_buf(struct virtqueue *_vq,
+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.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;
-
-add_head:
- /* Set token. */
- vq->data[head] = data;
-
- /* Put entry in available array (but don't update avail->idx until they
- * do sync). */
- avail = (vq->vring.avail->idx & (vq->vring.num-1));
- vq->vring.avail->ring[avail] = head;
-
- /* Descriptors and available array need to be set before we expose the
- * new available array entries. */
- virtio_wmb(vq);
- vq->vring.avail->idx++;
- vq->num_added++;
+ int ret;
- /* This is very unlikely, but theoretically possible. Kick
- * just in case. */
- if (unlikely(vq->num_added == (1 << 16) - 1))
- virtqueue_kick(_vq);
+ ret = virtqueue_start_buf(vq, data, out + in, !!out + !!in, gfp);
+ if (ret < 0)
+ return ret;
- pr_debug("Added buffer head %i to %p\n", head, vq);
- END_USE(vq);
+ if (out)
+ virtqueue_add_sg(vq, sg, out, DMA_TO_DEVICE);
+ if (in)
+ virtqueue_add_sg(vq, sg + out, in, DMA_FROM_DEVICE);
+ virtqueue_end_buf(vq);
return 0;
}
EXPORT_SYMBOL_GPL(virtqueue_add_buf);
@@ -537,8 +401,7 @@ EXPORT_SYMBOL_GPL(virtqueue_start_buf);
* @nents: the number of items to process in sgl
* @dir: whether the sgl is read or written (DMA_TO_DEVICE/DMA_FROM_DEVICE only)
*
- * Note that, unlike virtqueue_add_buf, this function follows chained
- * scatterlists, and stops before the @nents-th item if a scatterlist item
+ * This function will stop before the @nents-th item if a scatterlist item
* has a marker.
*
* Caller must ensure we don't call this with other virtqueue operations
--
1.7.1
--
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