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SubjectRe: [net-next RFC V5 4/5] virtio_net: multiqueue support
On Thu, Jul 05, 2012 at 06:29:53PM +0800, Jason Wang wrote:
> This patch converts virtio_net to a multi queue device. After negotiated
> VIRTIO_NET_F_MULTIQUEUE feature, the virtio device has many tx/rx queue pairs,
> and driver could read the number from config space.
>
> The driver expects the number of rx/tx queue paris is equal to the number of
> vcpus. To maximize the performance under this per-cpu rx/tx queue pairs, some
> optimization were introduced:
>
> - Txq selection is based on the processor id in order to avoid contending a lock
> whose owner may exits to host.
> - Since the txq/txq were per-cpu, affinity hint were set to the cpu that owns
> the queue pairs.
>
> Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Overall fine. I think it is best to smash the following patch
into this one, so that default behavior does not
jump to mq then back. some comments below: mostly nits, and a minor bug.

If you are worried the patch is too big, it can be split
differently
- rework to use send_queue/receive_queue structures, no
functional changes.
- add multiqueue

but this is not a must.

> ---
> drivers/net/virtio_net.c | 645 ++++++++++++++++++++++++++++++-------------
> include/linux/virtio_net.h | 2 +
> 2 files changed, 452 insertions(+), 195 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1db445b..7410187 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -26,6 +26,7 @@
> #include <linux/scatterlist.h>
> #include <linux/if_vlan.h>
> #include <linux/slab.h>
> +#include <linux/interrupt.h>
>
> static int napi_weight = 128;
> module_param(napi_weight, int, 0444);
> @@ -41,6 +42,8 @@ module_param(gso, bool, 0444);
> #define VIRTNET_SEND_COMMAND_SG_MAX 2
> #define VIRTNET_DRIVER_VERSION "1.0.0"
>
> +#define MAX_QUEUES 256
> +
> struct virtnet_stats {
> struct u64_stats_sync tx_syncp;
> struct u64_stats_sync rx_syncp;

Would be a bit better not to have artificial limits like that.
Maybe allocate arrays at probe time, then we can
take whatever the device gives us?

> @@ -51,43 +54,69 @@ struct virtnet_stats {
> u64 rx_packets;
> };
>
> -struct virtnet_info {
> - struct virtio_device *vdev;
> - struct virtqueue *rvq, *svq, *cvq;
> - struct net_device *dev;
> +/* Internal representation of a send virtqueue */
> +struct send_queue {
> + /* Virtqueue associated with this send _queue */
> + struct virtqueue *vq;
> +
> + /* TX: fragments + linear part + virtio header */
> + struct scatterlist sg[MAX_SKB_FRAGS + 2];
> +};
> +
> +/* Internal representation of a receive virtqueue */
> +struct receive_queue {
> + /* Virtqueue associated with this receive_queue */
> + struct virtqueue *vq;
> +
> + /* Back pointer to the virtnet_info */
> + struct virtnet_info *vi;
> +
> struct napi_struct napi;
> - unsigned int status;
>
> /* Number of input buffers, and max we've ever had. */
> unsigned int num, max;
>
> + /* Work struct for refilling if we run low on memory. */
> + struct delayed_work refill;
> +
> + /* Chain pages by the private ptr. */
> + struct page *pages;
> +
> + /* RX: fragments + linear part + virtio header */
> + struct scatterlist sg[MAX_SKB_FRAGS + 2];
> +};
> +
> +struct virtnet_info {
> + u16 num_queue_pairs; /* # of RX/TX vq pairs */
> +
> + struct send_queue *sq[MAX_QUEUES] ____cacheline_aligned_in_smp;
> + struct receive_queue *rq[MAX_QUEUES] ____cacheline_aligned_in_smp;

The assumption is a tx/rx pair is handled on the same cpu, yes?
If yes maybe make it a single array to improve cache locality
a bit?
struct queue_pair {
struct send_queue sq;
struct receive_queue rq;
};

> + struct virtqueue *cvq;
> +
> + struct virtio_device *vdev;
> + struct net_device *dev;
> + unsigned int status;
> +
> /* I like... big packets and I cannot lie! */
> bool big_packets;
>
> /* Host will merge rx buffers for big packets (shake it! shake it!) */
> bool mergeable_rx_bufs;
>
> + /* Has control virtqueue */
> + bool has_cvq;
> +

won't checking (cvq != NULL) be enough?

> /* enable config space updates */
> bool config_enable;
>
> /* Active statistics */
> struct virtnet_stats __percpu *stats;
>
> - /* Work struct for refilling if we run low on memory. */
> - struct delayed_work refill;
> -
> /* Work struct for config space updates */
> struct work_struct config_work;
>
> /* Lock for config space updates */
> struct mutex config_lock;
> -
> - /* Chain pages by the private ptr. */
> - struct page *pages;
> -
> - /* fragments + linear part + virtio header */
> - struct scatterlist rx_sg[MAX_SKB_FRAGS + 2];
> - struct scatterlist tx_sg[MAX_SKB_FRAGS + 2];
> };
>
> struct skb_vnet_hdr {
> @@ -108,6 +137,22 @@ struct padded_vnet_hdr {
> char padding[6];
> };
>
> +static inline int txq_get_qnum(struct virtnet_info *vi, struct virtqueue *vq)
> +{
> + int ret = virtqueue_get_queue_index(vq);
> +
> + /* skip ctrl vq */
> + if (vi->has_cvq)
> + return (ret - 1) / 2;
> + else
> + return ret / 2;
> +}
> +
> +static inline int rxq_get_qnum(struct virtnet_info *vi, struct virtqueue *vq)
> +{
> + return virtqueue_get_queue_index(vq) / 2;
> +}
> +
> static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
> {
> return (struct skb_vnet_hdr *)skb->cb;
> @@ -117,22 +162,22 @@ static inline struct skb_vnet_hdr *skb_vnet_hdr(struct sk_buff *skb)
> * private is used to chain pages for big packets, put the whole
> * most recent used list in the beginning for reuse
> */
> -static void give_pages(struct virtnet_info *vi, struct page *page)
> +static void give_pages(struct receive_queue *rq, struct page *page)
> {
> struct page *end;
>
> /* Find end of list, sew whole thing into vi->pages. */
> for (end = page; end->private; end = (struct page *)end->private);
> - end->private = (unsigned long)vi->pages;
> - vi->pages = page;
> + end->private = (unsigned long)rq->pages;
> + rq->pages = page;
> }
>
> -static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
> +static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
> {
> - struct page *p = vi->pages;
> + struct page *p = rq->pages;
>
> if (p) {
> - vi->pages = (struct page *)p->private;
> + rq->pages = (struct page *)p->private;
> /* clear private here, it is used to chain pages */
> p->private = 0;
> } else
> @@ -140,15 +185,15 @@ static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
> return p;
> }
>
> -static void skb_xmit_done(struct virtqueue *svq)
> +static void skb_xmit_done(struct virtqueue *vq)
> {
> - struct virtnet_info *vi = svq->vdev->priv;
> + struct virtnet_info *vi = vq->vdev->priv;
>
> /* Suppress further interrupts. */
> - virtqueue_disable_cb(svq);
> + virtqueue_disable_cb(vq);
>
> /* We were probably waiting for more output buffers. */
> - netif_wake_queue(vi->dev);
> + netif_wake_subqueue(vi->dev, txq_get_qnum(vi, vq));
> }
>
> static void set_skb_frag(struct sk_buff *skb, struct page *page,
> @@ -167,9 +212,10 @@ static void set_skb_frag(struct sk_buff *skb, struct page *page,
> }
>
> /* Called from bottom half context */
> -static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> +static struct sk_buff *page_to_skb(struct receive_queue *rq,
> struct page *page, unsigned int len)
> {
> + struct virtnet_info *vi = rq->vi;
> struct sk_buff *skb;
> struct skb_vnet_hdr *hdr;
> unsigned int copy, hdr_len, offset;
> @@ -225,12 +271,12 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
> }
>
> if (page)
> - give_pages(vi, page);
> + give_pages(rq, page);
>
> return skb;
> }
>
> -static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
> +static int receive_mergeable(struct receive_queue *rq, struct sk_buff *skb)
> {
> struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
> struct page *page;
> @@ -244,7 +290,7 @@ static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
> skb->dev->stats.rx_length_errors++;
> return -EINVAL;
> }
> - page = virtqueue_get_buf(vi->rvq, &len);
> + page = virtqueue_get_buf(rq->vq, &len);
> if (!page) {
> pr_debug("%s: rx error: %d buffers missing\n",
> skb->dev->name, hdr->mhdr.num_buffers);
> @@ -257,13 +303,14 @@ static int receive_mergeable(struct virtnet_info *vi, struct sk_buff *skb)
>
> set_skb_frag(skb, page, 0, &len);
>
> - --vi->num;
> + --rq->num;
> }
> return 0;
> }
>
> -static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
> +static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
> {
> + struct net_device *dev = rq->vi->dev;
> struct virtnet_info *vi = netdev_priv(dev);
> struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
> struct sk_buff *skb;
> @@ -274,7 +321,7 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
> pr_debug("%s: short packet %i\n", dev->name, len);
> dev->stats.rx_length_errors++;
> if (vi->mergeable_rx_bufs || vi->big_packets)
> - give_pages(vi, buf);
> + give_pages(rq, buf);
> else
> dev_kfree_skb(buf);
> return;
> @@ -286,14 +333,14 @@ static void receive_buf(struct net_device *dev, void *buf, unsigned int len)
> skb_trim(skb, len);
> } else {
> page = buf;
> - skb = page_to_skb(vi, page, len);
> + skb = page_to_skb(rq, page, len);
> if (unlikely(!skb)) {
> dev->stats.rx_dropped++;
> - give_pages(vi, page);
> + give_pages(rq, page);
> return;
> }
> if (vi->mergeable_rx_bufs)
> - if (receive_mergeable(vi, skb)) {
> + if (receive_mergeable(rq, skb)) {
> dev_kfree_skb(skb);
> return;
> }
> @@ -363,90 +410,91 @@ frame_err:
> dev_kfree_skb(skb);
> }
>
> -static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
> +static int add_recvbuf_small(struct receive_queue *rq, gfp_t gfp)
> {
> struct sk_buff *skb;
> struct skb_vnet_hdr *hdr;
> int err;
>
> - skb = __netdev_alloc_skb_ip_align(vi->dev, MAX_PACKET_LEN, gfp);
> + skb = __netdev_alloc_skb_ip_align(rq->vi->dev, MAX_PACKET_LEN, gfp);
> if (unlikely(!skb))
> return -ENOMEM;
>
> skb_put(skb, MAX_PACKET_LEN);
>
> hdr = skb_vnet_hdr(skb);
> - sg_set_buf(vi->rx_sg, &hdr->hdr, sizeof hdr->hdr);
> + sg_set_buf(rq->sg, &hdr->hdr, sizeof hdr->hdr);
> +
> + skb_to_sgvec(skb, rq->sg + 1, 0, skb->len);
>
> - skb_to_sgvec(skb, vi->rx_sg + 1, 0, skb->len);
> + err = virtqueue_add_buf(rq->vq, rq->sg, 0, 2, skb, gfp);
>
> - err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 2, skb, gfp);
> if (err < 0)
> dev_kfree_skb(skb);
>
> return err;
> }
>
> -static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
> +static int add_recvbuf_big(struct receive_queue *rq, gfp_t gfp)
> {
> struct page *first, *list = NULL;
> char *p;
> int i, err, offset;
>
> - /* page in vi->rx_sg[MAX_SKB_FRAGS + 1] is list tail */
> + /* page in rq->sg[MAX_SKB_FRAGS + 1] is list tail */
> for (i = MAX_SKB_FRAGS + 1; i > 1; --i) {
> - first = get_a_page(vi, gfp);
> + first = get_a_page(rq, gfp);
> if (!first) {
> if (list)
> - give_pages(vi, list);
> + give_pages(rq, list);
> return -ENOMEM;
> }
> - sg_set_buf(&vi->rx_sg[i], page_address(first), PAGE_SIZE);
> + sg_set_buf(&rq->sg[i], page_address(first), PAGE_SIZE);
>
> /* chain new page in list head to match sg */
> first->private = (unsigned long)list;
> list = first;
> }
>
> - first = get_a_page(vi, gfp);
> + first = get_a_page(rq, gfp);
> if (!first) {
> - give_pages(vi, list);
> + give_pages(rq, list);
> return -ENOMEM;
> }
> p = page_address(first);
>
> - /* vi->rx_sg[0], vi->rx_sg[1] share the same page */
> - /* a separated vi->rx_sg[0] for virtio_net_hdr only due to QEMU bug */
> - sg_set_buf(&vi->rx_sg[0], p, sizeof(struct virtio_net_hdr));
> + /* rq->sg[0], rq->sg[1] share the same page */
> + /* a separated rq->sg[0] for virtio_net_hdr only due to QEMU bug */
> + sg_set_buf(&rq->sg[0], p, sizeof(struct virtio_net_hdr));
>
> - /* vi->rx_sg[1] for data packet, from offset */
> + /* rq->sg[1] for data packet, from offset */
> offset = sizeof(struct padded_vnet_hdr);
> - sg_set_buf(&vi->rx_sg[1], p + offset, PAGE_SIZE - offset);
> + sg_set_buf(&rq->sg[1], p + offset, PAGE_SIZE - offset);
>
> /* chain first in list head */
> first->private = (unsigned long)list;
> - err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, MAX_SKB_FRAGS + 2,
> + err = virtqueue_add_buf(rq->vq, rq->sg, 0, MAX_SKB_FRAGS + 2,
> first, gfp);
> if (err < 0)
> - give_pages(vi, first);
> + give_pages(rq, first);
>
> return err;
> }
>
> -static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
> +static int add_recvbuf_mergeable(struct receive_queue *rq, gfp_t gfp)
> {
> struct page *page;
> int err;
>
> - page = get_a_page(vi, gfp);
> + page = get_a_page(rq, gfp);
> if (!page)
> return -ENOMEM;
>
> - sg_init_one(vi->rx_sg, page_address(page), PAGE_SIZE);
> + sg_init_one(rq->sg, page_address(page), PAGE_SIZE);
>
> - err = virtqueue_add_buf(vi->rvq, vi->rx_sg, 0, 1, page, gfp);
> + err = virtqueue_add_buf(rq->vq, rq->sg, 0, 1, page, gfp);
> if (err < 0)
> - give_pages(vi, page);
> + give_pages(rq, page);
>
> return err;
> }
> @@ -458,97 +506,104 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
> * before we're receiving packets, or from refill_work which is
> * careful to disable receiving (using napi_disable).
> */
> -static bool try_fill_recv(struct virtnet_info *vi, gfp_t gfp)
> +static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
> {
> + struct virtnet_info *vi = rq->vi;
> int err;
> bool oom;
>
> do {
> if (vi->mergeable_rx_bufs)
> - err = add_recvbuf_mergeable(vi, gfp);
> + err = add_recvbuf_mergeable(rq, gfp);
> else if (vi->big_packets)
> - err = add_recvbuf_big(vi, gfp);
> + err = add_recvbuf_big(rq, gfp);
> else
> - err = add_recvbuf_small(vi, gfp);
> + err = add_recvbuf_small(rq, gfp);
>
> oom = err == -ENOMEM;
> if (err < 0)
> break;
> - ++vi->num;
> + ++rq->num;
> } while (err > 0);
> - if (unlikely(vi->num > vi->max))
> - vi->max = vi->num;
> - virtqueue_kick(vi->rvq);
> + if (unlikely(rq->num > rq->max))
> + rq->max = rq->num;
> + virtqueue_kick(rq->vq);
> return !oom;
> }
>
> -static void skb_recv_done(struct virtqueue *rvq)
> +static void skb_recv_done(struct virtqueue *vq)
> {
> - struct virtnet_info *vi = rvq->vdev->priv;
> + struct virtnet_info *vi = vq->vdev->priv;
> + struct napi_struct *napi = &vi->rq[rxq_get_qnum(vi, vq)]->napi;
> +
> /* Schedule NAPI, Suppress further interrupts if successful. */
> - if (napi_schedule_prep(&vi->napi)) {
> - virtqueue_disable_cb(rvq);
> - __napi_schedule(&vi->napi);
> + if (napi_schedule_prep(napi)) {
> + virtqueue_disable_cb(vq);
> + __napi_schedule(napi);
> }
> }
>
> -static void virtnet_napi_enable(struct virtnet_info *vi)
> +static void virtnet_napi_enable(struct receive_queue *rq)
> {
> - napi_enable(&vi->napi);
> + napi_enable(&rq->napi);
>
> /* If all buffers were filled by other side before we napi_enabled, we
> * won't get another interrupt, so process any outstanding packets
> * now. virtnet_poll wants re-enable the queue, so we disable here.
> * We synchronize against interrupts via NAPI_STATE_SCHED */
> - if (napi_schedule_prep(&vi->napi)) {
> - virtqueue_disable_cb(vi->rvq);
> + if (napi_schedule_prep(&rq->napi)) {
> + virtqueue_disable_cb(rq->vq);
> local_bh_disable();
> - __napi_schedule(&vi->napi);
> + __napi_schedule(&rq->napi);
> local_bh_enable();
> }
> }
>
> static void refill_work(struct work_struct *work)
> {
> - struct virtnet_info *vi;
> + struct napi_struct *napi;
> + struct receive_queue *rq;
> bool still_empty;
>
> - vi = container_of(work, struct virtnet_info, refill.work);
> - napi_disable(&vi->napi);
> - still_empty = !try_fill_recv(vi, GFP_KERNEL);
> - virtnet_napi_enable(vi);
> + rq = container_of(work, struct receive_queue, refill.work);
> + napi = &rq->napi;
> +
> + napi_disable(napi);
> + still_empty = !try_fill_recv(rq, GFP_KERNEL);
> + virtnet_napi_enable(rq);
>
> /* In theory, this can happen: if we don't get any buffers in
> * we will *never* try to fill again. */
> if (still_empty)
> - queue_delayed_work(system_nrt_wq, &vi->refill, HZ/2);
> + queue_delayed_work(system_nrt_wq, &rq->refill, HZ/2);
> }
>
> static int virtnet_poll(struct napi_struct *napi, int budget)
> {
> - struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
> + struct receive_queue *rq = container_of(napi, struct receive_queue,
> + napi);
> void *buf;
> unsigned int len, received = 0;
>
> again:
> while (received < budget &&
> - (buf = virtqueue_get_buf(vi->rvq, &len)) != NULL) {
> - receive_buf(vi->dev, buf, len);
> - --vi->num;
> + (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> + receive_buf(rq, buf, len);
> + --rq->num;
> received++;
> }
>
> - if (vi->num < vi->max / 2) {
> - if (!try_fill_recv(vi, GFP_ATOMIC))
> - queue_delayed_work(system_nrt_wq, &vi->refill, 0);
> + if (rq->num < rq->max / 2) {
> + if (!try_fill_recv(rq, GFP_ATOMIC))
> + queue_delayed_work(system_nrt_wq, &rq->refill, 0);
> }
>
> /* Out of packets? */
> if (received < budget) {
> napi_complete(napi);
> - if (unlikely(!virtqueue_enable_cb(vi->rvq)) &&
> + if (unlikely(!virtqueue_enable_cb(rq->vq)) &&
> napi_schedule_prep(napi)) {
> - virtqueue_disable_cb(vi->rvq);
> + virtqueue_disable_cb(rq->vq);
> __napi_schedule(napi);
> goto again;
> }
> @@ -557,13 +612,14 @@ again:
> return received;
> }
>
> -static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
> +static unsigned int free_old_xmit_skbs(struct virtnet_info *vi,
> + struct virtqueue *vq)
> {
> struct sk_buff *skb;
> unsigned int len, tot_sgs = 0;
> struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
>
> - while ((skb = virtqueue_get_buf(vi->svq, &len)) != NULL) {
> + while ((skb = virtqueue_get_buf(vq, &len)) != NULL) {
> pr_debug("Sent skb %p\n", skb);
>
> u64_stats_update_begin(&stats->tx_syncp);
> @@ -577,7 +633,8 @@ static unsigned int free_old_xmit_skbs(struct virtnet_info *vi)
> return tot_sgs;
> }
>
> -static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
> +static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb,
> + struct virtqueue *vq, struct scatterlist *sg)
> {
> struct skb_vnet_hdr *hdr = skb_vnet_hdr(skb);
> const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;
> @@ -615,44 +672,47 @@ static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
>
> /* Encode metadata header at front. */
> if (vi->mergeable_rx_bufs)
> - sg_set_buf(vi->tx_sg, &hdr->mhdr, sizeof hdr->mhdr);
> + sg_set_buf(sg, &hdr->mhdr, sizeof hdr->mhdr);
> else
> - sg_set_buf(vi->tx_sg, &hdr->hdr, sizeof hdr->hdr);
> + sg_set_buf(sg, &hdr->hdr, sizeof hdr->hdr);
>
> - hdr->num_sg = skb_to_sgvec(skb, vi->tx_sg + 1, 0, skb->len) + 1;
> - return virtqueue_add_buf(vi->svq, vi->tx_sg, hdr->num_sg,
> + hdr->num_sg = skb_to_sgvec(skb, sg + 1, 0, skb->len) + 1;
> + return virtqueue_add_buf(vq, sg, hdr->num_sg,
> 0, skb, GFP_ATOMIC);
> }
>
> static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> + int qnum = skb_get_queue_mapping(skb);
> + struct virtqueue *vq = vi->sq[qnum]->vq;
> int capacity;
>
> /* Free up any pending old buffers before queueing new ones. */
> - free_old_xmit_skbs(vi);
> + free_old_xmit_skbs(vi, vq);
>
> /* Try to transmit */
> - capacity = xmit_skb(vi, skb);
> + capacity = xmit_skb(vi, skb, vq, vi->sq[qnum]->sg);
>
> /* This can happen with OOM and indirect buffers. */
> if (unlikely(capacity < 0)) {
> if (likely(capacity == -ENOMEM)) {
> if (net_ratelimit())
> dev_warn(&dev->dev,
> - "TX queue failure: out of memory\n");
> + "TXQ (%d) failure: out of memory\n",
> + qnum);
> } else {
> dev->stats.tx_fifo_errors++;
> if (net_ratelimit())
> dev_warn(&dev->dev,
> - "Unexpected TX queue failure: %d\n",
> - capacity);
> + "Unexpected TXQ (%d) failure: %d\n",
> + qnum, capacity);
> }
> dev->stats.tx_dropped++;
> kfree_skb(skb);
> return NETDEV_TX_OK;
> }
> - virtqueue_kick(vi->svq);
> + virtqueue_kick(vq);
>
> /* Don't wait up for transmitted skbs to be freed. */
> skb_orphan(skb);
> @@ -661,13 +721,13 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> /* Apparently nice girls don't return TX_BUSY; stop the queue
> * before it gets out of hand. Naturally, this wastes entries. */
> if (capacity < 2+MAX_SKB_FRAGS) {
> - netif_stop_queue(dev);
> - if (unlikely(!virtqueue_enable_cb_delayed(vi->svq))) {
> + netif_stop_subqueue(dev, qnum);
> + if (unlikely(!virtqueue_enable_cb_delayed(vq))) {
> /* More just got used, free them then recheck. */
> - capacity += free_old_xmit_skbs(vi);
> + capacity += free_old_xmit_skbs(vi, vq);
> if (capacity >= 2+MAX_SKB_FRAGS) {
> - netif_start_queue(dev);
> - virtqueue_disable_cb(vi->svq);
> + netif_start_subqueue(dev, qnum);
> + virtqueue_disable_cb(vq);
> }
> }
> }
> @@ -700,7 +760,8 @@ static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
> unsigned int start;
>
> for_each_possible_cpu(cpu) {
> - struct virtnet_stats *stats = per_cpu_ptr(vi->stats, cpu);
> + struct virtnet_stats __percpu *stats
> + = per_cpu_ptr(vi->stats, cpu);
> u64 tpackets, tbytes, rpackets, rbytes;
>
> do {
> @@ -734,20 +795,26 @@ static struct rtnl_link_stats64 *virtnet_stats(struct net_device *dev,
> static void virtnet_netpoll(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> + int i;
>
> - napi_schedule(&vi->napi);
> + for (i = 0; i < vi->num_queue_pairs; i++)
> + napi_schedule(&vi->rq[i]->napi);
> }
> #endif
>
> static int virtnet_open(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> + int i;
>
> - /* Make sure we have some buffers: if oom use wq. */
> - if (!try_fill_recv(vi, GFP_KERNEL))
> - queue_delayed_work(system_nrt_wq, &vi->refill, 0);
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + /* Make sure we have some buffers: if oom use wq. */
> + if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
> + queue_delayed_work(system_nrt_wq,
> + &vi->rq[i]->refill, 0);
> + virtnet_napi_enable(vi->rq[i]);
> + }
>
> - virtnet_napi_enable(vi);
> return 0;
> }
>
> @@ -809,10 +876,13 @@ static void virtnet_ack_link_announce(struct virtnet_info *vi)
> static int virtnet_close(struct net_device *dev)
> {
> struct virtnet_info *vi = netdev_priv(dev);
> + int i;
>
> /* Make sure refill_work doesn't re-enable napi! */
> - cancel_delayed_work_sync(&vi->refill);
> - napi_disable(&vi->napi);
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + cancel_delayed_work_sync(&vi->rq[i]->refill);
> + napi_disable(&vi->rq[i]->napi);
> + }
>
> return 0;
> }
> @@ -924,11 +994,10 @@ static void virtnet_get_ringparam(struct net_device *dev,
> {
> struct virtnet_info *vi = netdev_priv(dev);
>
> - ring->rx_max_pending = virtqueue_get_vring_size(vi->rvq);
> - ring->tx_max_pending = virtqueue_get_vring_size(vi->svq);
> + ring->rx_max_pending = virtqueue_get_vring_size(vi->rq[0]->vq);
> + ring->tx_max_pending = virtqueue_get_vring_size(vi->sq[0]->vq);
> ring->rx_pending = ring->rx_max_pending;
> ring->tx_pending = ring->tx_max_pending;
> -
> }
>
>
> @@ -961,6 +1030,19 @@ static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
> return 0;
> }
>
> +/* To avoid contending a lock hold by a vcpu who would exit to host, select the
> + * txq based on the processor id.
> + */
> +static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb)
> +{
> + int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) :
> + smp_processor_id();
> +
> + while (unlikely(txq >= dev->real_num_tx_queues))
> + txq -= dev->real_num_tx_queues;
> + return txq;
> +}
> +
> static const struct net_device_ops virtnet_netdev = {
> .ndo_open = virtnet_open,
> .ndo_stop = virtnet_close,
> @@ -972,6 +1054,7 @@ static const struct net_device_ops virtnet_netdev = {
> .ndo_get_stats64 = virtnet_stats,
> .ndo_vlan_rx_add_vid = virtnet_vlan_rx_add_vid,
> .ndo_vlan_rx_kill_vid = virtnet_vlan_rx_kill_vid,
> + .ndo_select_queue = virtnet_select_queue,
> #ifdef CONFIG_NET_POLL_CONTROLLER
> .ndo_poll_controller = virtnet_netpoll,
> #endif
> @@ -1007,10 +1090,10 @@ static void virtnet_config_changed_work(struct work_struct *work)
>
> if (vi->status & VIRTIO_NET_S_LINK_UP) {
> netif_carrier_on(vi->dev);
> - netif_wake_queue(vi->dev);
> + netif_tx_wake_all_queues(vi->dev);
> } else {
> netif_carrier_off(vi->dev);
> - netif_stop_queue(vi->dev);
> + netif_tx_stop_all_queues(vi->dev);
> }
> done:
> mutex_unlock(&vi->config_lock);
> @@ -1023,41 +1106,217 @@ static void virtnet_config_changed(struct virtio_device *vdev)
> queue_work(system_nrt_wq, &vi->config_work);
> }
>
> -static int init_vqs(struct virtnet_info *vi)
> +static void free_receive_bufs(struct virtnet_info *vi)
> +{
> + int i;
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + while (vi->rq[i]->pages)
> + __free_pages(get_a_page(vi->rq[i], GFP_KERNEL), 0);
> + }
> +}
> +
> +/* Free memory allocated for send and receive queues */
> +static void virtnet_free_queues(struct virtnet_info *vi)
> {
> - struct virtqueue *vqs[3];
> - vq_callback_t *callbacks[] = { skb_recv_done, skb_xmit_done, NULL};
> - const char *names[] = { "input", "output", "control" };
> - int nvqs, err;
> + int i;
>
> - /* We expect two virtqueues, receive then send,
> - * and optionally control. */
> - nvqs = virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) ? 3 : 2;
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + kfree(vi->rq[i]);
> + vi->rq[i] = NULL;
> + kfree(vi->sq[i]);
> + vi->sq[i] = NULL;
> + }
> +}
>
> - err = vi->vdev->config->find_vqs(vi->vdev, nvqs, vqs, callbacks, names);
> - if (err)
> - return err;
> +static void free_unused_bufs(struct virtnet_info *vi)
> +{
> + void *buf;
> + int i;
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + struct virtqueue *vq = vi->sq[i]->vq;
> +
> + while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
> + dev_kfree_skb(buf);
> + }
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + struct virtqueue *vq = vi->rq[i]->vq;
> +
> + while ((buf = virtqueue_detach_unused_buf(vq)) != NULL) {
> + if (vi->mergeable_rx_bufs || vi->big_packets)
> + give_pages(vi->rq[i], buf);
> + else
> + dev_kfree_skb(buf);
> + --vi->rq[i]->num;
> + }
> + BUG_ON(vi->rq[i]->num != 0);
> + }
> +}
> +
> +static void virtnet_set_affinity(struct virtnet_info *vi, bool set)
> +{
> + int i;
> +
> + if (vi->num_queue_pairs == 1)
> + return;
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + int cpu = set ? i : -1;
> + virtqueue_set_affinity(vi->rq[i]->vq, cpu);
> + virtqueue_set_affinity(vi->sq[i]->vq, cpu);
> + }
> + return;
> +}
> +
> +static void virtnet_del_vqs(struct virtnet_info *vi)
> +{
> + struct virtio_device *vdev = vi->vdev;
> +
> + virtnet_set_affinity(vi, false);
> +
> + vdev->config->del_vqs(vdev);
> +
> + virtnet_free_queues(vi);
> +}
> +
> +static int virtnet_find_vqs(struct virtnet_info *vi)
> +{
> + vq_callback_t **callbacks;
> + struct virtqueue **vqs;
> + int ret = -ENOMEM;
> + int i, total_vqs;
> + char **names;
>
> - vi->rvq = vqs[0];
> - vi->svq = vqs[1];
> + /*
> + * We expect 1 RX virtqueue followed by 1 TX virtqueue, followd by
> + * possible control virtqueue and followed by the same
> + * 'vi->num_queue_pairs-1' more times
> + */
> + total_vqs = vi->num_queue_pairs * 2 +
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ);
> +
> + /* Allocate space for find_vqs parameters */
> + vqs = kmalloc(total_vqs * sizeof(*vqs), GFP_KERNEL);
> + callbacks = kmalloc(total_vqs * sizeof(*callbacks), GFP_KERNEL);
> + names = kmalloc(total_vqs * sizeof(*names), GFP_KERNEL);

so this needs to be kzalloc otherwise on an error cleanup will
get uninitialized data and crash?

> + if (!vqs || !callbacks || !names)
> + goto err;
> +
> + /* Parameters for control virtqueue, if any */
> + if (vi->has_cvq) {
> + callbacks[2] = NULL;
> + names[2] = "control";
> + }
> +
> + /* Allocate/initialize parameters for send/receive virtqueues */
> + for (i = 0; i < vi->num_queue_pairs * 2; i += 2) {
> + int j = (i == 0 ? i : i + vi->has_cvq);
> + callbacks[j] = skb_recv_done;
> + callbacks[j + 1] = skb_xmit_done;
> + names[j] = kasprintf(GFP_KERNEL, "input.%d", i / 2);
> + names[j + 1] = kasprintf(GFP_KERNEL, "output.%d", i / 2);

This needs wrappers. E.g. virtnet_rx_vq(int queue_pair), virtnet_tx_vq(int queue_pair);
Then you would just scan 0 to num_queue_pairs, and i is queue pair
number.

> + }
>
> - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ)) {
> + ret = vi->vdev->config->find_vqs(vi->vdev, total_vqs, vqs, callbacks,
> + (const char **)names);
> + if (ret)
> + goto err;
> +
> + if (vi->has_cvq)
> vi->cvq = vqs[2];
>
> - if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
> - vi->dev->features |= NETIF_F_HW_VLAN_FILTER;
> + for (i = 0; i < vi->num_queue_pairs * 2; i += 2) {
> + int j = i == 0 ? i : i + vi->has_cvq;
> + vi->rq[i / 2]->vq = vqs[j];
> + vi->sq[i / 2]->vq = vqs[j + 1];

Same here.

> }
> - return 0;
> +
> +err:
> + if (ret && names)

If we are here ret != 0. For names, just add another label, don't
complicate cleanup.

> + for (i = 0; i < vi->num_queue_pairs * 2; i++)
> + kfree(names[i]);
> +
> + kfree(names);
> + kfree(callbacks);
> + kfree(vqs);
> +
> + return ret;
> +}
> +
> +static int virtnet_alloc_queues(struct virtnet_info *vi)
> +{
> + int ret = -ENOMEM;
> + int i;
> +
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + vi->rq[i] = kzalloc(sizeof(*vi->rq[i]), GFP_KERNEL);
> + vi->sq[i] = kzalloc(sizeof(*vi->sq[i]), GFP_KERNEL);
> + if (!vi->rq[i] || !vi->sq[i])
> + goto err;
> + }
> +
> + ret = 0;
> +
> + /* setup initial receive and send queue parameters */
> + for (i = 0; i < vi->num_queue_pairs; i++) {
> + vi->rq[i]->vi = vi;
> + vi->rq[i]->pages = NULL;
> + INIT_DELAYED_WORK(&vi->rq[i]->refill, refill_work);
> + netif_napi_add(vi->dev, &vi->rq[i]->napi, virtnet_poll,
> + napi_weight);
> +
> + sg_init_table(vi->rq[i]->sg, ARRAY_SIZE(vi->rq[i]->sg));
> + sg_init_table(vi->sq[i]->sg, ARRAY_SIZE(vi->sq[i]->sg));
> + }
> +

Add return 0 here, then ret = 0 will not be needed
above and if (ret) below.


> +err:
> + if (ret)
> + virtnet_free_queues(vi);
> +
> + return ret;
> +}
> +
> +static int virtnet_setup_vqs(struct virtnet_info *vi)
> +{
> + int ret;
> +
> + /* Allocate send & receive queues */
> + ret = virtnet_alloc_queues(vi);
> + if (!ret) {
> + ret = virtnet_find_vqs(vi);
> + if (ret)
> + virtnet_free_queues(vi);
> + else
> + virtnet_set_affinity(vi, true);
> + }
> +
> + return ret;

Add some labels for error handling, this if nesting is messy.

> }
>
> static int virtnet_probe(struct virtio_device *vdev)
> {
> - int err;
> + int i, err;
> struct net_device *dev;
> struct virtnet_info *vi;
> + u16 num_queues, num_queue_pairs;
> +
> + /* Find if host supports multiqueue virtio_net device */
> + err = virtio_config_val(vdev, VIRTIO_NET_F_MULTIQUEUE,
> + offsetof(struct virtio_net_config,
> + num_queues), &num_queues);
> +
> + /* We need atleast 2 queue's */

typo

> + if (err || num_queues < 2)
> + num_queues = 2;
> + if (num_queues > MAX_QUEUES * 2)
> + num_queues = MAX_QUEUES;
> +
> + num_queue_pairs = num_queues / 2;
>
> /* Allocate ourselves a network device with room for our info */
> - dev = alloc_etherdev(sizeof(struct virtnet_info));
> + dev = alloc_etherdev_mq(sizeof(struct virtnet_info), num_queue_pairs);
> if (!dev)
> return -ENOMEM;
>
> @@ -1103,22 +1362,18 @@ static int virtnet_probe(struct virtio_device *vdev)
>
> /* Set up our device-specific information */
> vi = netdev_priv(dev);
> - netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
> vi->dev = dev;
> vi->vdev = vdev;
> vdev->priv = vi;
> - vi->pages = NULL;
> vi->stats = alloc_percpu(struct virtnet_stats);
> err = -ENOMEM;
> if (vi->stats == NULL)
> - goto free;
> + goto free_netdev;
>
> - INIT_DELAYED_WORK(&vi->refill, refill_work);
> mutex_init(&vi->config_lock);
> vi->config_enable = true;
> INIT_WORK(&vi->config_work, virtnet_config_changed_work);
> - sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
> - sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
> + vi->num_queue_pairs = num_queue_pairs;
>
> /* If we can receive ANY GSO packets, we must allocate large ones. */
> if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> @@ -1129,9 +1384,17 @@ static int virtnet_probe(struct virtio_device *vdev)
> if (virtio_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF))
> vi->mergeable_rx_bufs = true;
>
> - err = init_vqs(vi);
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
> + vi->has_cvq = true;
> +

How about we disable multiqueue if there's no cvq?
Will make logic a bit simpler, won't it?

> + /* Allocate/initialize the rx/tx queues, and invoke find_vqs */
> + err = virtnet_setup_vqs(vi);
> if (err)
> - goto free_stats;
> + goto free_netdev;
> +
> + if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ) &&
> + virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VLAN))
> + dev->features |= NETIF_F_HW_VLAN_FILTER;
>
> err = register_netdev(dev);
> if (err) {
> @@ -1140,12 +1403,15 @@ static int virtnet_probe(struct virtio_device *vdev)
> }
>
> /* Last of all, set up some receive buffers. */
> - try_fill_recv(vi, GFP_KERNEL);
> -
> - /* If we didn't even get one input buffer, we're useless. */
> - if (vi->num == 0) {
> - err = -ENOMEM;
> - goto unregister;
> + for (i = 0; i < num_queue_pairs; i++) {
> + try_fill_recv(vi->rq[i], GFP_KERNEL);
> +
> + /* If we didn't even get one input buffer, we're useless. */
> + if (vi->rq[i]->num == 0) {
> + free_unused_bufs(vi);
> + err = -ENOMEM;
> + goto free_recv_bufs;
> + }
> }
>
> /* Assume link up if device can't report link status,
> @@ -1158,42 +1424,25 @@ static int virtnet_probe(struct virtio_device *vdev)
> netif_carrier_on(dev);
> }
>
> - pr_debug("virtnet: registered device %s\n", dev->name);
> + pr_debug("virtnet: registered device %s with %d RX and TX vq's\n",
> + dev->name, num_queue_pairs);
> +
> return 0;
>
> -unregister:
> +free_recv_bufs:
> + free_receive_bufs(vi);
> unregister_netdev(dev);
> +
> free_vqs:
> - vdev->config->del_vqs(vdev);
> -free_stats:
> - free_percpu(vi->stats);
> -free:
> + for (i = 0; i < num_queue_pairs; i++)
> + cancel_delayed_work_sync(&vi->rq[i]->refill);
> + virtnet_del_vqs(vi);
> +
> +free_netdev:
> free_netdev(dev);
> return err;
> }
>
> -static void free_unused_bufs(struct virtnet_info *vi)
> -{
> - void *buf;
> - while (1) {
> - buf = virtqueue_detach_unused_buf(vi->svq);
> - if (!buf)
> - break;
> - dev_kfree_skb(buf);
> - }
> - while (1) {
> - buf = virtqueue_detach_unused_buf(vi->rvq);
> - if (!buf)
> - break;
> - if (vi->mergeable_rx_bufs || vi->big_packets)
> - give_pages(vi, buf);
> - else
> - dev_kfree_skb(buf);
> - --vi->num;
> - }
> - BUG_ON(vi->num != 0);
> -}
> -
> static void remove_vq_common(struct virtnet_info *vi)
> {
> vi->vdev->config->reset(vi->vdev);
> @@ -1201,10 +1450,9 @@ static void remove_vq_common(struct virtnet_info *vi)
> /* Free unused buffers in both send and recv, if any. */
> free_unused_bufs(vi);
>
> - vi->vdev->config->del_vqs(vi->vdev);
> + free_receive_bufs(vi);
>
> - while (vi->pages)
> - __free_pages(get_a_page(vi, GFP_KERNEL), 0);
> + virtnet_del_vqs(vi);
> }
>
> static void __devexit virtnet_remove(struct virtio_device *vdev)
> @@ -1230,6 +1478,7 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
> static int virtnet_freeze(struct virtio_device *vdev)
> {
> struct virtnet_info *vi = vdev->priv;
> + int i;
>
> /* Prevent config work handler from accessing the device */
> mutex_lock(&vi->config_lock);
> @@ -1237,10 +1486,13 @@ static int virtnet_freeze(struct virtio_device *vdev)
> mutex_unlock(&vi->config_lock);
>
> netif_device_detach(vi->dev);
> - cancel_delayed_work_sync(&vi->refill);
> + for (i = 0; i < vi->num_queue_pairs; i++)
> + cancel_delayed_work_sync(&vi->rq[i]->refill);
>
> if (netif_running(vi->dev))
> - napi_disable(&vi->napi);
> + for (i = 0; i < vi->num_queue_pairs; i++)
> + napi_disable(&vi->rq[i]->napi);
> +
>
> remove_vq_common(vi);
>
> @@ -1252,19 +1504,22 @@ static int virtnet_freeze(struct virtio_device *vdev)
> static int virtnet_restore(struct virtio_device *vdev)
> {
> struct virtnet_info *vi = vdev->priv;
> - int err;
> + int err, i;
>
> - err = init_vqs(vi);
> + err = virtnet_setup_vqs(vi);
> if (err)
> return err;
>
> if (netif_running(vi->dev))
> - virtnet_napi_enable(vi);
> + for (i = 0; i < vi->num_queue_pairs; i++)
> + virtnet_napi_enable(vi->rq[i]);
>
> netif_device_attach(vi->dev);
>
> - if (!try_fill_recv(vi, GFP_KERNEL))
> - queue_delayed_work(system_nrt_wq, &vi->refill, 0);
> + for (i = 0; i < vi->num_queue_pairs; i++)
> + if (!try_fill_recv(vi->rq[i], GFP_KERNEL))
> + queue_delayed_work(system_nrt_wq,
> + &vi->rq[i]->refill, 0);
>
> mutex_lock(&vi->config_lock);
> vi->config_enable = true;
> @@ -1287,7 +1542,7 @@ static unsigned int features[] = {
> VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
> VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
> VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
> - VIRTIO_NET_F_GUEST_ANNOUNCE,
> + VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MULTIQUEUE,
> };
>
> static struct virtio_driver virtio_net_driver = {
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 1bc7e30..60f09ff 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -61,6 +61,8 @@ struct virtio_net_config {
> __u8 mac[6];
> /* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
> __u16 status;
> + /* Total number of RX/TX queues */
> + __u16 num_queues;
> } __attribute__((packed));
>
> /* This is the first element of the scatter-gather list. If you don't
> --
> 1.7.1


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