On Tue, Jun 11, 2024 at 07:41:40PM +0800, Xuan Zhuo wrote:
> If the xsk is enabling, the xsk tx will share the send queue.
> But the xsk requires that the send queue use the premapped mode.
> So the send queue must support premapped mode when it is bound to
> af-xdp.
>
> * virtnet_sq_set_premapped(sq, true) is used to enable premapped mode.
>
> In this mode, the driver will record the dma info when skb or xdp
> frame is sent.
>
> Currently, the SQ premapped mode is operational only with af-xdp. In
> this mode, af-xdp, the kernel stack, and xdp tx/redirect will share
> the same SQ. Af-xdp independently manages its DMA. The kernel stack
> and xdp tx/redirect utilize this DMA metadata to manage the DMA
> info.
>
> If the indirect descriptor feature be supported, the volume of DMA
> details we need to maintain becomes quite substantial. Here, we have
> a cap on the amount of DMA info we manage.
>
> If the kernel stack and xdp tx/redirect attempt to use more
> descriptors, virtnet_add_outbuf() will return an -ENOMEM error. But
> the af-xdp can work continually.
>
> * virtnet_sq_set_premapped(sq, false) is used to disable premapped mode.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 219 ++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 215 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e84a4624549b..4968ab7eb5a4 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -25,6 +25,7 @@
> #include <net/net_failover.h>
> #include <net/netdev_rx_queue.h>
> #include <net/netdev_queues.h>
> +#include <uapi/linux/virtio_ring.h>
>
> static int napi_weight = NAPI_POLL_WEIGHT;
> module_param(napi_weight, int, 0444);
> @@ -276,6 +277,25 @@ struct virtnet_rq_dma {
> u16 need_sync;
> };
>
> +struct virtnet_sq_dma {
> + union {
> + struct virtnet_sq_dma *next;
Maybe:
struct llist_node node;
I'd like to avoid growing our own single linked list
implementation if at all possible.
> + void *data;
> + };
> + dma_addr_t addr;
> + u32 len;
> + u8 num;
> +};
> +
> +struct virtnet_sq_dma_info {
> + /* record for kfree */
> + void *p;
> +
> + u32 free_num;
> +
> + struct virtnet_sq_dma *free;
> +};
> +
> /* Internal representation of a send virtqueue */
> struct send_queue {
> /* Virtqueue associated with this send _queue */
> @@ -295,6 +315,11 @@ struct send_queue {
>
> /* Record whether sq is in reset state. */
> bool reset;
> +
> + /* SQ is premapped mode or not. */
> + bool premapped;
> +
> + struct virtnet_sq_dma_info dmainfo;
> };
>
> /* Internal representation of a receive virtqueue */
> @@ -492,9 +517,11 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
> enum virtnet_xmit_type {
> VIRTNET_XMIT_TYPE_SKB,
> VIRTNET_XMIT_TYPE_XDP,
> + VIRTNET_XMIT_TYPE_DMA,
> };
>
> -#define VIRTNET_XMIT_TYPE_MASK (VIRTNET_XMIT_TYPE_SKB | VIRTNET_XMIT_TYPE_XDP)
> +#define VIRTNET_XMIT_TYPE_MASK (VIRTNET_XMIT_TYPE_SKB | VIRTNET_XMIT_TYPE_XDP \
> + | VIRTNET_XMIT_TYPE_DMA)
>
> static enum virtnet_xmit_type virtnet_xmit_ptr_strip(void **ptr)
> {
> @@ -510,12 +537,178 @@ static void *virtnet_xmit_ptr_mix(void *ptr, enum virtnet_xmit_type type)
> return (void *)((unsigned long)ptr | type);
> }
>
> +static void virtnet_sq_unmap(struct send_queue *sq, void **data)
> +{
> + struct virtnet_sq_dma *head, *tail, *p;
> + int i;
> +
> + head = *data;
> +
> + p = head;
> +
> + for (i = 0; i < head->num; ++i) {
> + virtqueue_dma_unmap_page_attrs(sq->vq, p->addr, p->len,
> + DMA_TO_DEVICE, 0);
> + tail = p;
> + p = p->next;
> + }
> +
> + *data = tail->data;
> +
> + tail->next = sq->dmainfo.free;
> + sq->dmainfo.free = head;
> + sq->dmainfo.free_num += head->num;
> +}
> +
> +static void *virtnet_dma_chain_update(struct send_queue *sq,
> + struct virtnet_sq_dma *head,
> + struct virtnet_sq_dma *tail,
> + u8 num, void *data)
> +{
> + sq->dmainfo.free = tail->next;
> + sq->dmainfo.free_num -= num;
> + head->num = num;
> +
> + tail->data = data;
> +
> + return virtnet_xmit_ptr_mix(head, VIRTNET_XMIT_TYPE_DMA);
> +}
> +
> +static struct virtnet_sq_dma *virtnet_sq_map_sg(struct send_queue *sq, int num, void *data)
> +{
> + struct virtnet_sq_dma *head, *tail, *p;
> + struct scatterlist *sg;
> + dma_addr_t addr;
> + int i, err;
> +
> + if (num > sq->dmainfo.free_num)
> + return NULL;
> +
> + head = sq->dmainfo.free;
> + p = head;
> +
> + tail = NULL;
> +
> + for (i = 0; i < num; ++i) {
> + sg = &sq->sg[i];
> +
> + addr = virtqueue_dma_map_page_attrs(sq->vq, sg_page(sg),
> + sg->offset,
> + sg->length, DMA_TO_DEVICE,
> + 0);
> + err = virtqueue_dma_mapping_error(sq->vq, addr);
> + if (err)
> + goto err;
> +
> + sg->dma_address = addr;
> +
> + tail = p;
> + tail->addr = sg->dma_address;
> + tail->len = sg->length;
> +
> + p = p->next;
> + }
> +
> + return virtnet_dma_chain_update(sq, head, tail, num, data);
> +
> +err:
> + if (tail) {
> + virtnet_dma_chain_update(sq, head, tail, i, data);
> + virtnet_sq_unmap(sq, (void **)&head);
> + }
> +
> + return NULL;
> +}
> +
> static int virtnet_add_outbuf(struct send_queue *sq, int num, void *data,
> enum virtnet_xmit_type type)
> {
> - return virtqueue_add_outbuf(sq->vq, sq->sg, num,
> - virtnet_xmit_ptr_mix(data, type),
> - GFP_ATOMIC);
> + int ret;
> +
> + data = virtnet_xmit_ptr_mix(data, type);
> +
> + if (sq->premapped) {
> + data = virtnet_sq_map_sg(sq, num, data);
> + if (!data)
> + return -ENOMEM;
> + }
> +
> + ret = virtqueue_add_outbuf(sq->vq, sq->sg, num, data, GFP_ATOMIC);
> + if (ret && sq->premapped) {
> + virtnet_xmit_ptr_strip(&data);
> + virtnet_sq_unmap(sq, &data);
> + }
> +
> + return ret;
> +}
> +
> +static int virtnet_sq_alloc_dma_meta(struct send_queue *sq)
> +{
> + struct virtnet_sq_dma *d;
> + int num, i;
> +
> + num = virtqueue_get_vring_size(sq->vq);
> +
> + /* Currently, the SQ premapped mode is operational only with af-xdp. In
> + * this mode, af-xdp, the kernel stack, and xdp tx/redirect will share
> + * the same SQ. Af-xdp independently manages its DMA. The kernel stack
> + * and xdp tx/redirect utilize this DMA metadata to manage the DMA info.
> + *
> + * If the indirect descriptor feature be supported, the volume of DMA
> + * details we need to maintain becomes quite substantial. Here, we have
> + * a cap on the amount of DMA info we manage, effectively limiting it to
> + * twice the size of the ring buffer.
> + *
> + * If the kernel stack and xdp tx/redirect attempt to use more
> + * descriptors than allowed by this double ring buffer size,
> + * virtnet_add_outbuf() will return an -ENOMEM error. But the af-xdp can
> + * work continually.
> + */
> + if (virtio_has_feature(sq->vq->vdev, VIRTIO_RING_F_INDIRECT_DESC))
> + num = num * 2;
> +
> + sq->dmainfo.free = kcalloc(num, sizeof(*sq->dmainfo.free), GFP_KERNEL);
Can be large. kvmalloc seems more appropriate.
> + if (!sq->dmainfo.free)
> + return -ENOMEM;
> +
> + sq->dmainfo.p = sq->dmainfo.free;
> + sq->dmainfo.free_num = num;
> +
> + for (i = 0; i < num; ++i) {
> + d = &sq->dmainfo.free[i];
> + d->next = d + 1;
> + }
> +
> + d->next = NULL;
> +
> + return 0;
> +}
> +
> +static void virtnet_sq_free_dma_meta(struct send_queue *sq)
> +{
> + kfree(sq->dmainfo.p);
> +
> + sq->dmainfo.p = NULL;
> + sq->dmainfo.free = NULL;
> + sq->dmainfo.free_num = 0;
> +}
> +
> +/* This function must be called immediately after creating the vq, or after vq
> + * reset, and before adding any buffers to it.
> + */
> +static int virtnet_sq_set_premapped(struct send_queue *sq, bool premapped)
> +{
> + if (premapped) {
> + if (virtnet_sq_alloc_dma_meta(sq))
> + return -ENOMEM;
I would just return what virtnet_sq_alloc_dma_meta returns.
int r = virtnet_sq_alloc_dma_meta();
if (r)
return r;
> + } else {
> + virtnet_sq_free_dma_meta(sq);
> + }
> +
> + BUG_ON(virtqueue_set_dma_premapped(sq->vq, premapped));
> +
> + sq->premapped = premapped;
> + return 0;
> }
>
> static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> @@ -529,6 +722,7 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
> ++stats->packets;
>
> +retry:
> switch (virtnet_xmit_ptr_strip(&ptr)) {
> case VIRTNET_XMIT_TYPE_SKB:
> skb = ptr;
> @@ -545,6 +739,10 @@ static void __free_old_xmit(struct send_queue *sq, bool in_napi,
> stats->bytes += xdp_get_frame_len(frame);
> xdp_return_frame(frame);
> break;
> +
> + case VIRTNET_XMIT_TYPE_DMA:
> + virtnet_sq_unmap(sq, &ptr);
> + goto retry;
> }
> }
> }
> @@ -5232,6 +5430,8 @@ static void virtnet_free_queues(struct virtnet_info *vi)
> for (i = 0; i < vi->max_queue_pairs; i++) {
> __netif_napi_del(&vi->rq[i].napi);
> __netif_napi_del(&vi->sq[i].napi);
> +
> + virtnet_sq_free_dma_meta(&vi->sq[i]);
> }
>
> /* We called __netif_napi_del(),
> @@ -5280,6 +5480,13 @@ static void free_receive_page_frags(struct virtnet_info *vi)
>
> static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> {
> + struct virtnet_info *vi = vq->vdev->priv;
> + struct send_queue *sq;
> + int i = vq2rxq(vq);
> +
> + sq = &vi->sq[i];
> +
> +retry:
> switch (virtnet_xmit_ptr_strip(&buf)) {
> case VIRTNET_XMIT_TYPE_SKB:
> dev_kfree_skb(buf);
> @@ -5288,6 +5495,10 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
> case VIRTNET_XMIT_TYPE_XDP:
> xdp_return_frame(buf);
> break;
> +
> + case VIRTNET_XMIT_TYPE_DMA:
> + virtnet_sq_unmap(sq, &buf);
> + goto retry;
document what's going on here? why are we retrying?
> }
> }
>
> --
> 2.32.0.3.g01195cf9f
