On Sat, Aug 16, 2025 at 1:59 AM Dragos Tatulea [off-list ref] wrote:

On Fri, Aug 15, 2025 at 11:05:56AM -0700, Mina Almasry wrote:

quoted

On Fri, Aug 15, 2025 at 4:07 AM Dragos Tatulea [off-list ref] wrote:

quoted

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@nvidia.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).

The bitmap API can handle any number of bits. Can it not?

Ah, yes, I missed this:

+       rxq_bitmap = bitmap_alloc(netdev->num_rx_queues, GFP_KERNEL);


Which allocates netdev->num_rx_queues bits. I was confused by the fact
that rxq_bitmap is an unsigned long * and thought that was the # of
bits in the map.

This patch should be good just with conversion to netdev->real_num_rx_queues.

-- 
Thanks,
Mina