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Commit 5a08b04f authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

virtio: allow extra context per descriptor 



Allow extra context per descriptor. To avoid slow down for data path,
this disables use of indirect descriptors for this vq.

Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 0a12ae40

drivers/virtio/virtio_ring.c

+57 −13
Original line number Diff line number Diff line
@@ -263,6 +263,7 @@ static inline int virtqueue_add(struct virtqueue *_vq, 
				unsigned int out_sgs,

				unsigned int in_sgs,

				void *data,

				void *ctx,

				gfp_t gfp)

{

	struct vring_virtqueue *vq = to_vvq(_vq);
@@ -275,6 +276,7 @@ static inline int virtqueue_add(struct virtqueue *_vq, 
	START_USE(vq);



	BUG_ON(data == NULL);

	BUG_ON(ctx && vq->indirect);



	if (unlikely(vq->broken)) {

		END_USE(vq);
@@ -389,6 +391,8 @@ static inline int virtqueue_add(struct virtqueue *_vq, 
	vq->desc_state[head].data = data;

	if (indirect)

		vq->desc_state[head].indir_desc = desc;

	if (ctx)

		vq->desc_state[head].indir_desc = ctx;



	/* Put entry in available array (but don't update avail->idx until they

	 * do sync). */
@@ -461,7 +465,8 @@ int virtqueue_add_sgs(struct virtqueue *_vq, 
		for (sg = sgs[i]; sg; sg = sg_next(sg))

			total_sg++;

	}

	return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);

	return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs,

			     data, NULL, gfp);

}

EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
@@ -483,7 +488,7 @@ int virtqueue_add_outbuf(struct virtqueue *vq, 
			 void *data,

			 gfp_t gfp)

{

	return virtqueue_add(vq, &sg, num, 1, 0, data, gfp);

	return virtqueue_add(vq, &sg, num, 1, 0, data, NULL, gfp);

}

EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
@@ -505,10 +510,34 @@ int virtqueue_add_inbuf(struct virtqueue *vq, 
			void *data,

			gfp_t gfp)

{

	return virtqueue_add(vq, &sg, num, 0, 1, data, gfp);

	return virtqueue_add(vq, &sg, num, 0, 1, data, NULL, gfp);

}

EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);



/**

 * virtqueue_add_inbuf_ctx - expose input buffers to other end

 * @vq: the struct virtqueue we're talking about.

 * @sg: scatterlist (must be well-formed and terminated!)

 * @num: the number of entries in @sg writable by other side

 * @data: the token identifying the buffer.

 * @ctx: extra context for the token

 * @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, EIO).

 */

int virtqueue_add_inbuf_ctx(struct virtqueue *vq,

			struct scatterlist *sg, unsigned int num,

			void *data,

			void *ctx,

			gfp_t gfp)

{

	return virtqueue_add(vq, &sg, num, 0, 1, data, ctx, gfp);

}

EXPORT_SYMBOL_GPL(virtqueue_add_inbuf_ctx);



/**

 * virtqueue_kick_prepare - first half of split virtqueue_kick call.

 * @vq: the struct virtqueue
@@ -598,7 +627,8 @@ bool virtqueue_kick(struct virtqueue *vq) 
}

EXPORT_SYMBOL_GPL(virtqueue_kick);



static void detach_buf(struct vring_virtqueue *vq, unsigned int head)

static void detach_buf(struct vring_virtqueue *vq, unsigned int head,

		       void **ctx)

{

	unsigned int i, j;

	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
@@ -622,10 +652,15 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head) 
	/* Plus final descriptor */

	vq->vq.num_free++;



	/* Free the indirect table, if any, now that it's unmapped. */

	if (vq->desc_state[head].indir_desc) {

	if (vq->indirect) {

		struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;

		u32 len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);

		u32 len;



		/* Free the indirect table, if any, now that it's unmapped. */

		if (!indir_desc)

			return;



		len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);



		BUG_ON(!(vq->vring.desc[head].flags &

			 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
@@ -634,8 +669,10 @@ static void detach_buf(struct vring_virtqueue *vq, unsigned int head) 
		for (j = 0; j < len / sizeof(struct vring_desc); j++)

			vring_unmap_one(vq, &indir_desc[j]);



		kfree(vq->desc_state[head].indir_desc);

		kfree(indir_desc);

		vq->desc_state[head].indir_desc = NULL;

	} else if (ctx) {

		*ctx = vq->desc_state[head].indir_desc;

	}

}
@@ -660,7 +697,8 @@ static inline bool more_used(const struct vring_virtqueue *vq) 
 * Returns NULL if there are no used buffers, or the "data" token

 * handed to virtqueue_add_*().

 */

void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)

void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,

			    void **ctx)

{

	struct vring_virtqueue *vq = to_vvq(_vq);

	void *ret;
@@ -698,7 +736,7 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) 


	/* detach_buf clears data, so grab it now. */

	ret = vq->desc_state[i].data;

	detach_buf(vq, i);

	detach_buf(vq, i, ctx);

	vq->last_used_idx++;

	/* If we expect an interrupt for the next entry, tell host

	 * by writing event index and flush out the write before
@@ -715,8 +753,13 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) 
	END_USE(vq);

	return ret;

}

EXPORT_SYMBOL_GPL(virtqueue_get_buf);

EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx);



void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)

{

	return virtqueue_get_buf_ctx(_vq, len, NULL);

}

EXPORT_SYMBOL_GPL(virtqueue_get_buf);

/**

 * virtqueue_disable_cb - disable callbacks

 * @vq: the struct virtqueue we're talking about.
@@ -878,7 +921,7 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq) 
			continue;

		/* detach_buf clears data, so grab it now. */

		buf = vq->desc_state[i].data;

		detach_buf(vq, i);

		detach_buf(vq, i, NULL);

		vq->avail_idx_shadow--;

		vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);

		END_USE(vq);
@@ -951,7 +994,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, 
	vq->last_add_time_valid = false;

#endif



	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);

	vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) &&

		!context;

	vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);



	/* No callback?  Tell other side not to bother us. */

include/linux/virtio.h

+9 −0
Original line number Diff line number Diff line
@@ -44,6 +44,12 @@ int virtqueue_add_inbuf(struct virtqueue *vq, 
			void *data,

			gfp_t gfp);



int virtqueue_add_inbuf_ctx(struct virtqueue *vq,

			    struct scatterlist sg[], unsigned int num,

			    void *data,

			    void *ctx,

			    gfp_t gfp);



int virtqueue_add_sgs(struct virtqueue *vq,

		      struct scatterlist *sgs[],

		      unsigned int out_sgs,
@@ -59,6 +65,9 @@ bool virtqueue_notify(struct virtqueue *vq); 


void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);



void *virtqueue_get_buf_ctx(struct virtqueue *vq, unsigned int *len,

			    void **ctx);



void virtqueue_disable_cb(struct virtqueue *vq);



bool virtqueue_enable_cb(struct virtqueue *vq);