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xsk: add new netlink attribute dedicated for ZC max frags
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Introduce new netlink attribute NETDEV_A_DEV_XDP_ZC_MAX_SEGS that will
carry maximum fragments that underlying ZC driver is able to handle on
TX side. It is going to be included in netlink response only when driver
supports ZC. Any value higher than 1 implies multi-buffer ZC support on
underlying device.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20230719132421.584801-11-maciej.fijalkowski@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Maciej Fijalkowski authored and Alexei Starovoitov committed Jul 19, 2023
1 parent 07428da commit 13ce2da
Showing 8 changed files with 25 additions and 1 deletion.
6 changes: 6 additions & 0 deletions Documentation/netlink/specs/netdev.yaml
Original file line number Diff line number Diff line change
@@ -62,6 +62,12 @@ attribute-sets:
type: u64
enum: xdp-act
enum-as-flags: true
-
name: xdp_zc_max_segs
doc: max fragment count supported by ZC driver
type: u32
checks:
min: 1

operations:
list:
1 change: 1 addition & 0 deletions include/linux/netdevice.h
Original file line number Diff line number Diff line change
@@ -2250,6 +2250,7 @@ struct net_device {
#define GRO_MAX_SIZE (8 * 65535u)
unsigned int gro_max_size;
unsigned int gro_ipv4_max_size;
unsigned int xdp_zc_max_segs;
rx_handler_func_t __rcu *rx_handler;
void __rcu *rx_handler_data;

1 change: 1 addition & 0 deletions include/uapi/linux/netdev.h
Original file line number Diff line number Diff line change
@@ -41,6 +41,7 @@ enum {
NETDEV_A_DEV_IFINDEX = 1,
NETDEV_A_DEV_PAD,
NETDEV_A_DEV_XDP_FEATURES,
NETDEV_A_DEV_XDP_ZC_MAX_SEGS,

__NETDEV_A_DEV_MAX,
NETDEV_A_DEV_MAX = (__NETDEV_A_DEV_MAX - 1)
1 change: 1 addition & 0 deletions net/core/dev.c
Original file line number Diff line number Diff line change
@@ -10613,6 +10613,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev_net_set(dev, &init_net);

dev->gso_max_size = GSO_LEGACY_MAX_SIZE;
dev->xdp_zc_max_segs = 1;
dev->gso_max_segs = GSO_MAX_SEGS;
dev->gro_max_size = GRO_LEGACY_MAX_SIZE;
dev->gso_ipv4_max_size = GSO_LEGACY_MAX_SIZE;
8 changes: 8 additions & 0 deletions net/core/netdev-genl.c
Original file line number Diff line number Diff line change
@@ -25,6 +25,14 @@ netdev_nl_dev_fill(struct net_device *netdev, struct sk_buff *rsp,
return -EINVAL;
}

if (netdev->xdp_features & NETDEV_XDP_ACT_XSK_ZEROCOPY) {
if (nla_put_u32(rsp, NETDEV_A_DEV_XDP_ZC_MAX_SEGS,
netdev->xdp_zc_max_segs)) {
genlmsg_cancel(rsp, hdr);
return -EINVAL;
}
}

genlmsg_end(rsp, hdr);

return 0;
1 change: 1 addition & 0 deletions tools/include/uapi/linux/netdev.h
Original file line number Diff line number Diff line change
@@ -41,6 +41,7 @@ enum {
NETDEV_A_DEV_IFINDEX = 1,
NETDEV_A_DEV_PAD,
NETDEV_A_DEV_XDP_FEATURES,
NETDEV_A_DEV_XDP_ZC_MAX_SEGS,

__NETDEV_A_DEV_MAX,
NETDEV_A_DEV_MAX = (__NETDEV_A_DEV_MAX - 1)
3 changes: 2 additions & 1 deletion tools/lib/bpf/libbpf.h
Original file line number Diff line number Diff line change
@@ -1105,9 +1105,10 @@ struct bpf_xdp_query_opts {
__u32 skb_prog_id; /* output */
__u8 attach_mode; /* output */
__u64 feature_flags; /* output */
__u32 xdp_zc_max_segs; /* output */
size_t :0;
};
#define bpf_xdp_query_opts__last_field feature_flags
#define bpf_xdp_query_opts__last_field xdp_zc_max_segs

LIBBPF_API int bpf_xdp_attach(int ifindex, int prog_fd, __u32 flags,
const struct bpf_xdp_attach_opts *opts);
5 changes: 5 additions & 0 deletions tools/lib/bpf/netlink.c
Original file line number Diff line number Diff line change
@@ -45,6 +45,7 @@ struct xdp_id_md {

struct xdp_features_md {
int ifindex;
__u32 xdp_zc_max_segs;
__u64 flags;
};

@@ -421,6 +422,9 @@ static int parse_xdp_features(struct nlmsghdr *nh, libbpf_dump_nlmsg_t fn,
return NL_CONT;

md->flags = libbpf_nla_getattr_u64(tb[NETDEV_A_DEV_XDP_FEATURES]);
if (tb[NETDEV_A_DEV_XDP_ZC_MAX_SEGS])
md->xdp_zc_max_segs =
libbpf_nla_getattr_u32(tb[NETDEV_A_DEV_XDP_ZC_MAX_SEGS]);
return NL_DONE;
}

@@ -493,6 +497,7 @@ int bpf_xdp_query(int ifindex, int xdp_flags, struct bpf_xdp_query_opts *opts)
return libbpf_err(err);

opts->feature_flags = md.flags;
opts->xdp_zc_max_segs = md.xdp_zc_max_segs;

skip_feature_flags:
return 0;

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