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Message-ID: <Y6GKN/1iOC9eTsEE@lore-desk>
Date: Tue, 20 Dec 2022 11:11:03 +0100
From: Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: Marek Majtyka <alardam@...il.com>,
Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
andrii@...nel.org, davem@...emloft.net, kuba@...nel.org,
hawk@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
toke@...hat.com, memxor@...il.com, saeedm@...dia.com,
anthony.l.nguyen@...el.com, gospo@...adcom.com,
vladimir.oltean@....com, nbd@....name, john@...ozen.org,
leon@...nel.org, simon.horman@...igine.com, aelior@...vell.com,
christophe.jaillet@...adoo.fr, ecree.xilinx@...il.com,
grygorii.strashko@...com, mst@...hat.com, bjorn@...nel.org,
magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
intel-wired-lan@...ts.osuosl.org
Subject: Re: [RFC bpf-next 2/8] net: introduce XDP features flag
On Dec 19, Stanislav Fomichev wrote:
> On Mon, Dec 19, 2022 at 3:51 PM Marek Majtyka <alardam@...il.com> wrote:
> >
> > At the time of writing, I wanted to be able to read additional information about the XDP capabilities of each network interface using ethtool. This change was intended for Linux users/admins, and not for XDP experts who mostly don't need it and prefer tasting XDP with netlink and bpf rather than reading network interface features with ethtool.
>
> Anything preventing ethtool from doing probing similar to 'bpftool
> feature probe'?
> The problem with these feature bits is that they might diverge and/or
> not work at all for the backported patches (where the fix/feature has
> been backported, but the part that exports the bit hasn't) :-(
> OTOH, I'm not sure we can probe everything from your list, but we
> might try and see what's missing..
Hi Stanislav,
I have not added the ethtool support to this series yet since userspace part is
still missing but I think we can consider XDP as a sort of sw offload so it
would be nice for the user/sysadmin (not xdp or bpf developer) to check the NIC
XDP capabilities similar to what we can already do for other hw offload
features.
Moreover let's consider XDP_REDIRECT of a scatter-gather XDP frame into a
devmap. I do not think there is a way to test if the 'target' device supports
SG and so we are forced to disable this feature until all drivers support it.
Introducing XDP features we can enable it on per-driver basis.
I think the same apply for other capabilities as well and just assuming a given
feature is not supported if an e2e test is not working seems a bit inaccurate.
Regards,
Lorenzo
>
> > On Mon, Dec 19, 2022 at 9:03 PM <sdf@...gle.com> wrote:
> >>
> >> On 12/19, Lorenzo Bianconi wrote:
> >> > From: Marek Majtyka <alardam@...il.com>
> >>
> >> > Implement support for checking what kind of XDP features a netdev
> >> > supports. Previously, there was no way to do this other than to try to
> >> > create an AF_XDP socket on the interface or load an XDP program and see
> >> > if it worked. This commit changes this by adding a new variable which
> >> > describes all xdp supported functions on pretty detailed level:
> >>
> >> > - aborted
> >> > - drop
> >> > - pass
> >> > - tx
> >> > - redirect
> >> > - sock_zerocopy
> >> > - hw_offload
> >> > - redirect_target
> >> > - tx_lock
> >> > - frag_rx
> >> > - frag_target
> >>
> >> > Zerocopy mode requires that redirect XDP operation is implemented in a
> >> > driver and the driver supports also zero copy mode. Full mode requires
> >> > that all XDP operation are implemented in the driver. Basic mode is just
> >> > full mode without redirect operation. Frag target requires
> >> > redirect_target one is supported by the driver.
> >>
> >> Can you share more about _why_ is it needed? If we can already obtain
> >> most of these signals via probing, why export the flags?
> >>
> >> > Initially, these new flags are disabled for all drivers by default.
> >>
> >> > Co-developed-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> >> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> >> > Co-developed-by: Lorenzo Bianconi <lorenzo@...nel.org>
> >> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> >> > Signed-off-by: Marek Majtyka <alardam@...il.com>
> >> > ---
> >> > .../networking/netdev-xdp-features.rst | 60 +++++++++++++++++
> >> > include/linux/netdevice.h | 2 +
> >> > include/linux/xdp_features.h | 64 +++++++++++++++++++
> >> > include/uapi/linux/if_link.h | 7 ++
> >> > include/uapi/linux/xdp_features.h | 34 ++++++++++
> >> > net/core/rtnetlink.c | 34 ++++++++++
> >> > tools/include/uapi/linux/if_link.h | 7 ++
> >> > tools/include/uapi/linux/xdp_features.h | 34 ++++++++++
> >> > 8 files changed, 242 insertions(+)
> >> > create mode 100644 Documentation/networking/netdev-xdp-features.rst
> >> > create mode 100644 include/linux/xdp_features.h
> >> > create mode 100644 include/uapi/linux/xdp_features.h
> >> > create mode 100644 tools/include/uapi/linux/xdp_features.h
> >>
> >> > diff --git a/Documentation/networking/netdev-xdp-features.rst
> >> > b/Documentation/networking/netdev-xdp-features.rst
> >> > new file mode 100644
> >> > index 000000000000..1dc803fe72dd
> >> > --- /dev/null
> >> > +++ b/Documentation/networking/netdev-xdp-features.rst
> >> > @@ -0,0 +1,60 @@
> >> > +.. SPDX-License-Identifier: GPL-2.0
> >> > +
> >> > +=====================
> >> > +Netdev XDP features
> >> > +=====================
> >> > +
> >> > + * XDP FEATURES FLAGS
> >> > +
> >> > +Following netdev xdp features flags can be retrieved over route netlink
> >> > +interface (compact form) - the same way as netdev feature flags.
> >> > +These features flags are read only and cannot be change at runtime.
> >> > +
> >> > +* XDP_ABORTED
> >> > +
> >> > +This feature informs if netdev supports xdp aborted action.
> >> > +
> >> > +* XDP_DROP
> >> > +
> >> > +This feature informs if netdev supports xdp drop action.
> >> > +
> >> > +* XDP_PASS
> >> > +
> >> > +This feature informs if netdev supports xdp pass action.
> >> > +
> >> > +* XDP_TX
> >> > +
> >> > +This feature informs if netdev supports xdp tx action.
> >> > +
> >> > +* XDP_REDIRECT
> >> > +
> >> > +This feature informs if netdev supports xdp redirect action.
> >> > +It assumes the all beforehand mentioned flags are enabled.
> >> > +
> >> > +* XDP_SOCK_ZEROCOPY
> >> > +
> >> > +This feature informs if netdev driver supports xdp zero copy.
> >> > +It assumes the all beforehand mentioned flags are enabled.
> >> > +
> >> > +* XDP_HW_OFFLOAD
> >> > +
> >> > +This feature informs if netdev driver supports xdp hw oflloading.
> >> > +
> >> > +* XDP_TX_LOCK
> >> > +
> >> > +This feature informs if netdev ndo_xdp_xmit function requires locking.
> >> > +
> >> > +* XDP_REDIRECT_TARGET
> >> > +
> >> > +This feature informs if netdev implements ndo_xdp_xmit callback.
> >> > +
> >> > +* XDP_FRAG_RX
> >> > +
> >> > +This feature informs if netdev implements non-linear xdp buff support in
> >> > +the driver napi callback.
> >> > +
> >> > +* XDP_FRAG_TARGET
> >> > +
> >> > +This feature informs if netdev implements non-linear xdp buff support in
> >> > +ndo_xdp_xmit callback. XDP_FRAG_TARGET requires XDP_REDIRECT_TARGET is
> >> > properly
> >> > +supported.
> >> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> >> > index aad12a179e54..ae5a8564383b 100644
> >> > --- a/include/linux/netdevice.h
> >> > +++ b/include/linux/netdevice.h
> >> > @@ -43,6 +43,7 @@
> >> > #include <net/xdp.h>
> >>
> >> > #include <linux/netdev_features.h>
> >> > +#include <linux/xdp_features.h>
> >> > #include <linux/neighbour.h>
> >> > #include <uapi/linux/netdevice.h>
> >> > #include <uapi/linux/if_bonding.h>
> >> > @@ -2362,6 +2363,7 @@ struct net_device {
> >> > struct rtnl_hw_stats64 *offload_xstats_l3;
> >>
> >> > struct devlink_port *devlink_port;
> >> > + xdp_features_t xdp_features;
> >> > };
> >> > #define to_net_dev(d) container_of(d, struct net_device, dev)
> >>
> >> > diff --git a/include/linux/xdp_features.h b/include/linux/xdp_features.h
> >> > new file mode 100644
> >> > index 000000000000..4e72a86ef329
> >> > --- /dev/null
> >> > +++ b/include/linux/xdp_features.h
> >> > @@ -0,0 +1,64 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> >> > +/*
> >> > + * Network device xdp features.
> >> > + */
> >> > +#ifndef _LINUX_XDP_FEATURES_H
> >> > +#define _LINUX_XDP_FEATURES_H
> >> > +
> >> > +#include <linux/types.h>
> >> > +#include <linux/bitops.h>
> >> > +#include <asm/byteorder.h>
> >> > +#include <uapi/linux/xdp_features.h>
> >> > +
> >> > +typedef u32 xdp_features_t;
> >> > +
> >> > +#define __XDP_F_BIT(bit) ((xdp_features_t)1 << (bit))
> >> > +#define __XDP_F(name) __XDP_F_BIT(XDP_F_##name##_BIT)
> >> > +
> >> > +#define XDP_F_ABORTED __XDP_F(ABORTED)
> >> > +#define XDP_F_DROP __XDP_F(DROP)
> >> > +#define XDP_F_PASS __XDP_F(PASS)
> >> > +#define XDP_F_TX __XDP_F(TX)
> >> > +#define XDP_F_REDIRECT __XDP_F(REDIRECT)
> >> > +#define XDP_F_REDIRECT_TARGET __XDP_F(REDIRECT_TARGET)
> >> > +#define XDP_F_SOCK_ZEROCOPY __XDP_F(SOCK_ZEROCOPY)
> >> > +#define XDP_F_HW_OFFLOAD __XDP_F(HW_OFFLOAD)
> >> > +#define XDP_F_TX_LOCK __XDP_F(TX_LOCK)
> >> > +#define XDP_F_FRAG_RX __XDP_F(FRAG_RX)
> >> > +#define XDP_F_FRAG_TARGET __XDP_F(FRAG_TARGET)
> >> > +
> >> > +#define XDP_F_BASIC (XDP_F_ABORTED | XDP_F_DROP | \
> >> > + XDP_F_PASS | XDP_F_TX)
> >> > +
> >> > +#define XDP_F_FULL (XDP_F_BASIC | XDP_F_REDIRECT)
> >> > +
> >> > +#define XDP_F_FULL_ZC (XDP_F_FULL | XDP_F_SOCK_ZEROCOPY)
> >> > +
> >> > +#define XDP_FEATURES_ABORTED_STR "xdp-aborted"
> >> > +#define XDP_FEATURES_DROP_STR "xdp-drop"
> >> > +#define XDP_FEATURES_PASS_STR "xdp-pass"
> >> > +#define XDP_FEATURES_TX_STR "xdp-tx"
> >> > +#define XDP_FEATURES_REDIRECT_STR "xdp-redirect"
> >> > +#define XDP_FEATURES_REDIRECT_TARGET_STR "xdp-redirect-target"
> >> > +#define XDP_FEATURES_SOCK_ZEROCOPY_STR "xdp-sock-zerocopy"
> >> > +#define XDP_FEATURES_HW_OFFLOAD_STR "xdp-hw-offload"
> >> > +#define XDP_FEATURES_TX_LOCK_STR "xdp-tx-lock"
> >> > +#define XDP_FEATURES_FRAG_RX_STR "xdp-frag-rx"
> >> > +#define XDP_FEATURES_FRAG_TARGET_STR "xdp-frag-target"
> >> > +
> >> > +#define DECLARE_XDP_FEATURES_TABLE(name, length) \
> >> > + const char name[][length] = { \
> >> > + [XDP_F_ABORTED_BIT] = XDP_FEATURES_ABORTED_STR, \
> >> > + [XDP_F_DROP_BIT] = XDP_FEATURES_DROP_STR, \
> >> > + [XDP_F_PASS_BIT] = XDP_FEATURES_PASS_STR, \
> >> > + [XDP_F_TX_BIT] = XDP_FEATURES_TX_STR, \
> >> > + [XDP_F_REDIRECT_BIT] = XDP_FEATURES_REDIRECT_STR, \
> >> > + [XDP_F_REDIRECT_TARGET_BIT] = XDP_FEATURES_REDIRECT_TARGET_STR, \
> >> > + [XDP_F_SOCK_ZEROCOPY_BIT] = XDP_FEATURES_SOCK_ZEROCOPY_STR, \
> >> > + [XDP_F_HW_OFFLOAD_BIT] = XDP_FEATURES_HW_OFFLOAD_STR, \
> >> > + [XDP_F_TX_LOCK_BIT] = XDP_FEATURES_TX_LOCK_STR, \
> >> > + [XDP_F_FRAG_RX_BIT] = XDP_FEATURES_FRAG_RX_STR, \
> >> > + [XDP_F_FRAG_TARGET_BIT] = XDP_FEATURES_FRAG_TARGET_STR, \
> >> > + }
> >> > +
> >> > +#endif /* _LINUX_XDP_FEATURES_H */
> >> > diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> >> > index 1021a7e47a86..971c658ceaea 100644
> >> > --- a/include/uapi/linux/if_link.h
> >> > +++ b/include/uapi/linux/if_link.h
> >> > @@ -374,6 +374,8 @@ enum {
> >>
> >> > IFLA_DEVLINK_PORT,
> >>
> >> > + IFLA_XDP_FEATURES,
> >> > +
> >> > __IFLA_MAX
> >> > };
> >>
> >> > @@ -1318,6 +1320,11 @@ enum {
> >>
> >> > #define IFLA_XDP_MAX (__IFLA_XDP_MAX - 1)
> >>
> >> > +enum {
> >> > + IFLA_XDP_FEATURES_WORD_UNSPEC = 0,
> >> > + IFLA_XDP_FEATURES_BITS_WORD,
> >> > +};
> >> > +
> >> > enum {
> >> > IFLA_EVENT_NONE,
> >> > IFLA_EVENT_REBOOT, /* internal reset / reboot */
> >> > diff --git a/include/uapi/linux/xdp_features.h
> >> > b/include/uapi/linux/xdp_features.h
> >> > new file mode 100644
> >> > index 000000000000..48eb42069bcd
> >> > --- /dev/null
> >> > +++ b/include/uapi/linux/xdp_features.h
> >> > @@ -0,0 +1,34 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> >> > +/*
> >> > + * Copyright (c) 2020 Intel
> >> > + */
> >> > +
> >> > +#ifndef __UAPI_LINUX_XDP_FEATURES__
> >> > +#define __UAPI_LINUX_XDP_FEATURES__
> >> > +
> >> > +enum {
> >> > + XDP_F_ABORTED_BIT,
> >> > + XDP_F_DROP_BIT,
> >> > + XDP_F_PASS_BIT,
> >> > + XDP_F_TX_BIT,
> >> > + XDP_F_REDIRECT_BIT,
> >> > + XDP_F_REDIRECT_TARGET_BIT,
> >> > + XDP_F_SOCK_ZEROCOPY_BIT,
> >> > + XDP_F_HW_OFFLOAD_BIT,
> >> > + XDP_F_TX_LOCK_BIT,
> >> > + XDP_F_FRAG_RX_BIT,
> >> > + XDP_F_FRAG_TARGET_BIT,
> >> > + /*
> >> > + * Add your fresh new property above and remember to update
> >> > + * documentation.
> >> > + */
> >> > + XDP_FEATURES_COUNT,
> >> > +};
> >> > +
> >> > +#define XDP_FEATURES_WORDS ((XDP_FEATURES_COUNT + 32 - 1) / 32)
> >> > +#define XDP_FEATURES_WORD(blocks, index) ((blocks)[(index) / 32U])
> >> > +#define XDP_FEATURES_FIELD_FLAG(index) (1U << (index) % 32U)
> >> > +#define XDP_FEATURES_BIT_IS_SET(blocks, index) \
> >> > + (XDP_FEATURES_WORD(blocks, index) & XDP_FEATURES_FIELD_FLAG(index))
> >> > +
> >> > +#endif /* __UAPI_LINUX_XDP_FEATURES__ */
> >> > diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> >> > index 64289bc98887..1c299746b614 100644
> >> > --- a/net/core/rtnetlink.c
> >> > +++ b/net/core/rtnetlink.c
> >> > @@ -1016,6 +1016,14 @@ static size_t rtnl_xdp_size(void)
> >> > return xdp_size;
> >> > }
> >>
> >> > +static size_t rtnl_xdp_features_size(void)
> >> > +{
> >> > + size_t xdp_size = nla_total_size(0) + /* nest IFLA_XDP_FEATURES */
> >> > + XDP_FEATURES_WORDS * nla_total_size(4);
> >> > +
> >> > + return xdp_size;
> >> > +}
> >> > +
> >> > static size_t rtnl_prop_list_size(const struct net_device *dev)
> >> > {
> >> > struct netdev_name_node *name_node;
> >> > @@ -1103,6 +1111,7 @@ static noinline size_t if_nlmsg_size(const struct
> >> > net_device *dev,
> >> > + rtnl_prop_list_size(dev)
> >> > + nla_total_size(MAX_ADDR_LEN) /* IFLA_PERM_ADDRESS */
> >> > + rtnl_devlink_port_size(dev)
> >> > + + rtnl_xdp_features_size() /* IFLA_XDP_FEATURES */
> >> > + 0;
> >> > }
> >>
> >> > @@ -1546,6 +1555,27 @@ static int rtnl_xdp_fill(struct sk_buff *skb,
> >> > struct net_device *dev)
> >> > return err;
> >> > }
> >>
> >> > +static int rtnl_xdp_features_fill(struct sk_buff *skb, struct net_device
> >> > *dev)
> >> > +{
> >> > + struct nlattr *attr;
> >> > +
> >> > + attr = nla_nest_start_noflag(skb, IFLA_XDP_FEATURES);
> >> > + if (!attr)
> >> > + return -EMSGSIZE;
> >> > +
> >> > + BUILD_BUG_ON(XDP_FEATURES_WORDS != 1);
> >> > + if (nla_put_u32(skb, IFLA_XDP_FEATURES_BITS_WORD, dev->xdp_features))
> >> > + goto err_cancel;
> >> > +
> >> > + nla_nest_end(skb, attr);
> >> > +
> >> > + return 0;
> >> > +
> >> > +err_cancel:
> >> > + nla_nest_cancel(skb, attr);
> >> > + return -EMSGSIZE;
> >> > +}
> >> > +
> >> > static u32 rtnl_get_event(unsigned long event)
> >> > {
> >> > u32 rtnl_event_type = IFLA_EVENT_NONE;
> >> > @@ -1904,6 +1934,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
> >> > if (rtnl_fill_devlink_port(skb, dev))
> >> > goto nla_put_failure;
> >>
> >> > + if (rtnl_xdp_features_fill(skb, dev))
> >> > + goto nla_put_failure;
> >> > +
> >> > nlmsg_end(skb, nlh);
> >> > return 0;
> >>
> >> > @@ -1968,6 +2001,7 @@ static const struct nla_policy
> >> > ifla_policy[IFLA_MAX+1] = {
> >> > [IFLA_TSO_MAX_SIZE] = { .type = NLA_REJECT },
> >> > [IFLA_TSO_MAX_SEGS] = { .type = NLA_REJECT },
> >> > [IFLA_ALLMULTI] = { .type = NLA_REJECT },
> >> > + [IFLA_XDP_FEATURES] = { .type = NLA_NESTED },
> >> > };
> >>
> >> > static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
> >> > diff --git a/tools/include/uapi/linux/if_link.h
> >> > b/tools/include/uapi/linux/if_link.h
> >> > index 82fe18f26db5..994228e9909a 100644
> >> > --- a/tools/include/uapi/linux/if_link.h
> >> > +++ b/tools/include/uapi/linux/if_link.h
> >> > @@ -354,6 +354,8 @@ enum {
> >>
> >> > IFLA_DEVLINK_PORT,
> >>
> >> > + IFLA_XDP_FEATURES,
> >> > +
> >> > __IFLA_MAX
> >> > };
> >>
> >> > @@ -1222,6 +1224,11 @@ enum {
> >>
> >> > #define IFLA_XDP_MAX (__IFLA_XDP_MAX - 1)
> >>
> >> > +enum {
> >> > + IFLA_XDP_FEATURES_WORD_UNSPEC = 0,
> >> > + IFLA_XDP_FEATURES_BITS_WORD,
> >> > +};
> >> > +
> >> > enum {
> >> > IFLA_EVENT_NONE,
> >> > IFLA_EVENT_REBOOT, /* internal reset / reboot */
> >> > diff --git a/tools/include/uapi/linux/xdp_features.h
> >> > b/tools/include/uapi/linux/xdp_features.h
> >> > new file mode 100644
> >> > index 000000000000..48eb42069bcd
> >> > --- /dev/null
> >> > +++ b/tools/include/uapi/linux/xdp_features.h
> >> > @@ -0,0 +1,34 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> >> > +/*
> >> > + * Copyright (c) 2020 Intel
> >> > + */
> >> > +
> >> > +#ifndef __UAPI_LINUX_XDP_FEATURES__
> >> > +#define __UAPI_LINUX_XDP_FEATURES__
> >> > +
> >> > +enum {
> >> > + XDP_F_ABORTED_BIT,
> >> > + XDP_F_DROP_BIT,
> >> > + XDP_F_PASS_BIT,
> >> > + XDP_F_TX_BIT,
> >> > + XDP_F_REDIRECT_BIT,
> >> > + XDP_F_REDIRECT_TARGET_BIT,
> >> > + XDP_F_SOCK_ZEROCOPY_BIT,
> >> > + XDP_F_HW_OFFLOAD_BIT,
> >> > + XDP_F_TX_LOCK_BIT,
> >> > + XDP_F_FRAG_RX_BIT,
> >> > + XDP_F_FRAG_TARGET_BIT,
> >> > + /*
> >> > + * Add your fresh new property above and remember to update
> >> > + * documentation.
> >> > + */
> >> > + XDP_FEATURES_COUNT,
> >> > +};
> >> > +
> >> > +#define XDP_FEATURES_WORDS ((XDP_FEATURES_COUNT + 32 - 1) / 32)
> >> > +#define XDP_FEATURES_WORD(blocks, index) ((blocks)[(index) / 32U])
> >> > +#define XDP_FEATURES_FIELD_FLAG(index) (1U << (index) % 32U)
> >> > +#define XDP_FEATURES_BIT_IS_SET(blocks, index) \
> >> > + (XDP_FEATURES_WORD(blocks, index) & XDP_FEATURES_FIELD_FLAG(index))
> >> > +
> >> > +#endif /* __UAPI_LINUX_XDP_FEATURES__ */
> >> > --
> >> > 2.38.1
> >>
>
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