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Message-ID: <CAHS8izM-2vdudZeRu51TNCRzVPQVBKmrj0YoK80nNgWvR-ft3g@mail.gmail.com>
Date: Fri, 15 Aug 2025 11:05:56 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: asml.silence@...il.com, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>, cratiu@...dia.com, tariqt@...dia.com, parav@...dia.com,
Christoph Hellwig <hch@...radead.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC net-next v3 6/7] net: devmem: pre-read requested rx queues
during bind
On Fri, Aug 15, 2025 at 4:07 AM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> Instead of reading the requested rx queues after binding the buffer,
> read the rx queues in advance in a bitmap and iterate over them when
> needed.
>
> This is a preparation for fetching the DMA device for each queue.
>
> This patch has no functional changes.
>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> ---
> net/core/netdev-genl.c | 76 +++++++++++++++++++++++++++---------------
> 1 file changed, 49 insertions(+), 27 deletions(-)
>
> diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> index 3e2d6aa6e060..3e990f100bf0 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -869,17 +869,50 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
> return err;
> }
>
> -int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> +static int netdev_nl_read_rxq_bitmap(struct genl_info *info,
> + unsigned long *rxq_bitmap)
> {
> struct nlattr *tb[ARRAY_SIZE(netdev_queue_id_nl_policy)];
> + struct nlattr *attr;
> + int rem, err = 0;
> + u32 rxq_idx;
> +
> + nla_for_each_attr_type(attr, NETDEV_A_DMABUF_QUEUES,
> + genlmsg_data(info->genlhdr),
> + genlmsg_len(info->genlhdr), rem) {
> + err = nla_parse_nested(
> + tb, ARRAY_SIZE(netdev_queue_id_nl_policy) - 1, attr,
> + netdev_queue_id_nl_policy, info->extack);
> + if (err < 0)
> + return err;
> +
> + if (NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_ID) ||
> + NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_TYPE))
> + return -EINVAL;
> +
> + if (nla_get_u32(tb[NETDEV_A_QUEUE_TYPE]) != NETDEV_QUEUE_TYPE_RX) {
> + NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_TYPE]);
> + return -EINVAL;
> + }
> +
> + rxq_idx = nla_get_u32(tb[NETDEV_A_QUEUE_ID]);
> +
> + bitmap_set(rxq_bitmap, rxq_idx, 1);
> + }
> +
> + return 0;
> +}
> +
> +int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> struct net_devmem_dmabuf_binding *binding;
> u32 ifindex, dmabuf_fd, rxq_idx;
> struct netdev_nl_sock *priv;
> struct net_device *netdev;
> + unsigned long *rxq_bitmap;
> struct device *dma_dev;
> struct sk_buff *rsp;
> - struct nlattr *attr;
> - int rem, err = 0;
> + int err = 0;
> void *hdr;
>
> if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_DEV_IFINDEX) ||
> @@ -922,37 +955,22 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> goto err_unlock;
> }
>
> + rxq_bitmap = bitmap_alloc(netdev->num_rx_queues, GFP_KERNEL);
> + if (!rxq_bitmap) {
> + err = -ENOMEM;
> + goto err_unlock;
> + }
> + netdev_nl_read_rxq_bitmap(info, rxq_bitmap);
> +
> dma_dev = netdev_queue_get_dma_dev(netdev, 0);
> binding = net_devmem_bind_dmabuf(netdev, dma_dev, DMA_FROM_DEVICE,
> dmabuf_fd, priv, info->extack);
> if (IS_ERR(binding)) {
> err = PTR_ERR(binding);
> - goto err_unlock;
> + goto err_rxq_bitmap;
> }
>
> - nla_for_each_attr_type(attr, NETDEV_A_DMABUF_QUEUES,
> - genlmsg_data(info->genlhdr),
> - genlmsg_len(info->genlhdr), rem) {
> - err = nla_parse_nested(
> - tb, ARRAY_SIZE(netdev_queue_id_nl_policy) - 1, attr,
> - netdev_queue_id_nl_policy, info->extack);
> - if (err < 0)
> - goto err_unbind;
> -
> - if (NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_ID) ||
> - NL_REQ_ATTR_CHECK(info->extack, attr, tb, NETDEV_A_QUEUE_TYPE)) {
> - err = -EINVAL;
> - goto err_unbind;
> - }
> -
> - if (nla_get_u32(tb[NETDEV_A_QUEUE_TYPE]) != NETDEV_QUEUE_TYPE_RX) {
> - NL_SET_BAD_ATTR(info->extack, tb[NETDEV_A_QUEUE_TYPE]);
> - err = -EINVAL;
> - goto err_unbind;
> - }
> -
> - rxq_idx = nla_get_u32(tb[NETDEV_A_QUEUE_ID]);
> -
> + for_each_set_bit(rxq_idx, rxq_bitmap, netdev->num_rx_queues) {
Is this code assuming that netdev->num_rx_queues (or
real_num_rx_queues) <= BITS_PER_ULONG? Aren't there devices out there
that support more than 64 hardware queues? If so, I guess you need a
different data structure than a bitmap (or maybe there is arbirary
sized bitmap library somewhere to use).
--
Thanks,
Mina
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