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Message-ID: <871s0q4p80.fsf@toke.dk>
Date: Wed, 22 May 2019 15:02:07 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Björn Töpel <bjorn.topel@...il.com>,
ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Cc: Björn Töpel <bjorn.topel@...el.com>,
magnus.karlsson@...el.com, brouer@...hat.com, bpf@...r.kernel.org,
jakub.kicinski@...ronome.com
Subject: Re: [PATCH bpf-next 1/2] net: xdp: refactor XDP_QUERY_PROG{,_HW} to netdev
Björn Töpel <bjorn.topel@...il.com> writes:
> From: Björn Töpel <bjorn.topel@...el.com>
>
> All XDP capable drivers need to implement the XDP_QUERY_PROG{,_HW}
> command of ndo_bpf. The query code is fairly generic. This commit
> refactors the query code up from the drivers to the netdev level.
>
> The struct net_device has gained four new members tracking the XDP
> program, the corresponding program flags, and which programs
> (SKB_MODE, DRV_MODE or HW_MODE) that are activated.
>
> The xdp_prog member, previously only used for SKB_MODE, is shared with
> DRV_MODE, since they are mutually exclusive.
>
> The program query operations is all done under the rtnl lock. However,
> the xdp_prog member is __rcu annotated, and used in a lock-less manner
> for the SKB_MODE. This is because the xdp_prog member is shared from a
> query program perspective (again, SKB and DRV are mutual exclusive),
> RCU read and assignments functions are still used when altering
> xdp_prog, even when only for queries in DRV_MODE. This is for
> sparse/lockdep correctness.
>
> A minor behavioral change was done during this refactorization; When
> passing a negative file descriptor to a netdev to disable XDP, the
> same program flag as the running program is required. An example.
>
> The eth0 is DRV_DRV capable. Previously, this was OK, but confusing:
>
> # ip link set dev eth0 xdp obj foo.o sec main
> # ip link set dev eth0 xdpgeneric off
>
> Now, the same commands give:
>
> # ip link set dev eth0 xdp obj foo.o sec main
> # ip link set dev eth0 xdpgeneric off
> Error: native and generic XDP can't be active at the same time.
>
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
Nice work!
Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
> include/linux/netdevice.h | 13 +++--
> net/core/dev.c | 120 ++++++++++++++++++++------------------
> net/core/rtnetlink.c | 33 ++---------
> 3 files changed, 76 insertions(+), 90 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 44b47e9df94a..bdcb20a3946c 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1940,6 +1940,11 @@ struct net_device {
> #endif
> struct hlist_node index_hlist;
>
> + struct bpf_prog *xdp_prog_hw;
> + unsigned int xdp_flags;
> + u32 xdp_prog_flags;
> + u32 xdp_prog_hw_flags;
> +
> /*
> * Cache lines mostly used on transmit path
> */
> @@ -2045,9 +2050,8 @@ struct net_device {
>
> static inline bool netif_elide_gro(const struct net_device *dev)
> {
> - if (!(dev->features & NETIF_F_GRO) || dev->xdp_prog)
> - return true;
> - return false;
> + return !(dev->features & NETIF_F_GRO) ||
> + dev->xdp_flags & XDP_FLAGS_SKB_MODE;
> }
>
> #define NETDEV_ALIGN 32
> @@ -3684,8 +3688,7 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
> typedef int (*bpf_op_t)(struct net_device *dev, struct netdev_bpf *bpf);
> int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
> int fd, u32 flags);
> -u32 __dev_xdp_query(struct net_device *dev, bpf_op_t xdp_op,
> - enum bpf_netdev_command cmd);
> +u32 dev_xdp_query(struct net_device *dev, unsigned int flags);
> int xdp_umem_query(struct net_device *dev, u16 queue_id);
>
> int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b6b8505cfb3e..ead16c3f955c 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -8005,31 +8005,31 @@ int dev_change_proto_down_generic(struct net_device *dev, bool proto_down)
> }
> EXPORT_SYMBOL(dev_change_proto_down_generic);
>
> -u32 __dev_xdp_query(struct net_device *dev, bpf_op_t bpf_op,
> - enum bpf_netdev_command cmd)
> +u32 dev_xdp_query(struct net_device *dev, unsigned int flags)
> {
> - struct netdev_bpf xdp;
> + struct bpf_prog *prog = NULL;
>
> - if (!bpf_op)
> + if (hweight32(flags) != 1)
> return 0;
>
> - memset(&xdp, 0, sizeof(xdp));
> - xdp.command = cmd;
> -
> - /* Query must always succeed. */
> - WARN_ON(bpf_op(dev, &xdp) < 0 && cmd == XDP_QUERY_PROG);
> + if (flags & (XDP_FLAGS_SKB_MODE | XDP_FLAGS_DRV_MODE))
> + prog = rtnl_dereference(dev->xdp_prog);
> + else if (flags & XDP_FLAGS_HW_MODE)
> + prog = dev->xdp_prog_hw;
>
> - return xdp.prog_id;
> + return prog ? prog->aux->id : 0;
> }
>
> -static int dev_xdp_install(struct net_device *dev, bpf_op_t bpf_op,
> +static int dev_xdp_install(struct net_device *dev, unsigned int target,
> struct netlink_ext_ack *extack, u32 flags,
> struct bpf_prog *prog)
> {
> + bpf_op_t bpf_op = dev->netdev_ops->ndo_bpf;
> struct netdev_bpf xdp;
> + int err;
>
> memset(&xdp, 0, sizeof(xdp));
> - if (flags & XDP_FLAGS_HW_MODE)
> + if (target == XDP_FLAGS_HW_MODE)
> xdp.command = XDP_SETUP_PROG_HW;
> else
> xdp.command = XDP_SETUP_PROG;
> @@ -8037,35 +8037,41 @@ static int dev_xdp_install(struct net_device *dev, bpf_op_t bpf_op,
> xdp.flags = flags;
> xdp.prog = prog;
>
> - return bpf_op(dev, &xdp);
> + err = (target == XDP_FLAGS_SKB_MODE) ?
> + generic_xdp_install(dev, &xdp) :
> + bpf_op(dev, &xdp);
> + if (!err) {
> + if (prog)
> + dev->xdp_flags |= target;
> + else
> + dev->xdp_flags &= ~target;
> +
> + if (target == XDP_FLAGS_HW_MODE) {
> + dev->xdp_prog_hw = prog;
> + dev->xdp_prog_hw_flags = flags;
> + } else if (target == XDP_FLAGS_DRV_MODE) {
> + rcu_assign_pointer(dev->xdp_prog, prog);
> + dev->xdp_prog_flags = flags;
> + }
> + }
> +
> + return err;
> }
>
> static void dev_xdp_uninstall(struct net_device *dev)
> {
> - struct netdev_bpf xdp;
> - bpf_op_t ndo_bpf;
> -
> - /* Remove generic XDP */
> - WARN_ON(dev_xdp_install(dev, generic_xdp_install, NULL, 0, NULL));
> -
> - /* Remove from the driver */
> - ndo_bpf = dev->netdev_ops->ndo_bpf;
> - if (!ndo_bpf)
> - return;
> -
> - memset(&xdp, 0, sizeof(xdp));
> - xdp.command = XDP_QUERY_PROG;
> - WARN_ON(ndo_bpf(dev, &xdp));
> - if (xdp.prog_id)
> - WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags,
> - NULL));
> -
> - /* Remove HW offload */
> - memset(&xdp, 0, sizeof(xdp));
> - xdp.command = XDP_QUERY_PROG_HW;
> - if (!ndo_bpf(dev, &xdp) && xdp.prog_id)
> - WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags,
> - NULL));
> + if (dev->xdp_flags & XDP_FLAGS_SKB_MODE) {
> + WARN_ON(dev_xdp_install(dev, XDP_FLAGS_SKB_MODE,
> + NULL, 0, NULL));
> + }
> + if (dev->xdp_flags & XDP_FLAGS_DRV_MODE) {
> + WARN_ON(dev_xdp_install(dev, XDP_FLAGS_DRV_MODE,
> + NULL, dev->xdp_prog_flags, NULL));
> + }
> + if (dev->xdp_flags & XDP_FLAGS_HW_MODE) {
> + WARN_ON(dev_xdp_install(dev, XDP_FLAGS_HW_MODE,
> + NULL, dev->xdp_prog_hw_flags, NULL));
> + }
> }
>
> /**
> @@ -8080,41 +8086,41 @@ static void dev_xdp_uninstall(struct net_device *dev)
> int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
> int fd, u32 flags)
> {
> - const struct net_device_ops *ops = dev->netdev_ops;
> - enum bpf_netdev_command query;
> + bool offload, drv_supp = !!dev->netdev_ops->ndo_bpf;
> struct bpf_prog *prog = NULL;
> - bpf_op_t bpf_op, bpf_chk;
> - bool offload;
> + unsigned int target;
> int err;
>
> ASSERT_RTNL();
>
> offload = flags & XDP_FLAGS_HW_MODE;
> - query = offload ? XDP_QUERY_PROG_HW : XDP_QUERY_PROG;
> + target = offload ? XDP_FLAGS_HW_MODE : XDP_FLAGS_DRV_MODE;
>
> - bpf_op = bpf_chk = ops->ndo_bpf;
> - if (!bpf_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE))) {
> + if (!drv_supp && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE))) {
> NL_SET_ERR_MSG(extack, "underlying driver does not support XDP in native mode");
> return -EOPNOTSUPP;
> }
> - if (!bpf_op || (flags & XDP_FLAGS_SKB_MODE))
> - bpf_op = generic_xdp_install;
> - if (bpf_op == bpf_chk)
> - bpf_chk = generic_xdp_install;
> +
> + if (!drv_supp || (flags & XDP_FLAGS_SKB_MODE))
> + target = XDP_FLAGS_SKB_MODE;
> +
> + if ((target == XDP_FLAGS_SKB_MODE &&
> + dev->xdp_flags & XDP_FLAGS_DRV_MODE) ||
> + (target == XDP_FLAGS_DRV_MODE &&
> + dev->xdp_flags & XDP_FLAGS_SKB_MODE)) {
> + NL_SET_ERR_MSG(extack, "native and generic XDP can't be active at the same time");
> + return -EEXIST;
> + }
>
> if (fd >= 0) {
> - if (!offload && __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG)) {
> - NL_SET_ERR_MSG(extack, "native and generic XDP can't be active at the same time");
> - return -EEXIST;
> - }
> - if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) &&
> - __dev_xdp_query(dev, bpf_op, query)) {
> + if (flags & XDP_FLAGS_UPDATE_IF_NOEXIST &&
> + dev_xdp_query(dev, target)) {
> NL_SET_ERR_MSG(extack, "XDP program already attached");
> return -EBUSY;
> }
>
> - prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
> - bpf_op == ops->ndo_bpf);
> + prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP, drv_supp);
> +
> if (IS_ERR(prog))
> return PTR_ERR(prog);
>
> @@ -8125,7 +8131,7 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
> }
> }
>
> - err = dev_xdp_install(dev, bpf_op, extack, flags, prog);
> + err = dev_xdp_install(dev, target, extack, flags, prog);
> if (err < 0 && prog)
> bpf_prog_put(prog);
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index adcc045952c2..99ca58db297f 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1360,37 +1360,14 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
> return 0;
> }
>
> -static u32 rtnl_xdp_prog_skb(struct net_device *dev)
> -{
> - const struct bpf_prog *generic_xdp_prog;
> -
> - ASSERT_RTNL();
> -
> - generic_xdp_prog = rtnl_dereference(dev->xdp_prog);
> - if (!generic_xdp_prog)
> - return 0;
> - return generic_xdp_prog->aux->id;
> -}
> -
> -static u32 rtnl_xdp_prog_drv(struct net_device *dev)
> -{
> - return __dev_xdp_query(dev, dev->netdev_ops->ndo_bpf, XDP_QUERY_PROG);
> -}
> -
> -static u32 rtnl_xdp_prog_hw(struct net_device *dev)
> -{
> - return __dev_xdp_query(dev, dev->netdev_ops->ndo_bpf,
> - XDP_QUERY_PROG_HW);
> -}
> -
> static int rtnl_xdp_report_one(struct sk_buff *skb, struct net_device *dev,
> u32 *prog_id, u8 *mode, u8 tgt_mode, u32 attr,
> - u32 (*get_prog_id)(struct net_device *dev))
> + unsigned int tgt_flags)
> {
> u32 curr_id;
> int err;
>
> - curr_id = get_prog_id(dev);
> + curr_id = dev_xdp_query(dev, tgt_flags);
> if (!curr_id)
> return 0;
>
> @@ -1421,15 +1398,15 @@ static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
> prog_id = 0;
> mode = XDP_ATTACHED_NONE;
> err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_SKB,
> - IFLA_XDP_SKB_PROG_ID, rtnl_xdp_prog_skb);
> + IFLA_XDP_SKB_PROG_ID, XDP_FLAGS_SKB_MODE);
> if (err)
> goto err_cancel;
> err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_DRV,
> - IFLA_XDP_DRV_PROG_ID, rtnl_xdp_prog_drv);
> + IFLA_XDP_DRV_PROG_ID, XDP_FLAGS_DRV_MODE);
> if (err)
> goto err_cancel;
> err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode, XDP_ATTACHED_HW,
> - IFLA_XDP_HW_PROG_ID, rtnl_xdp_prog_hw);
> + IFLA_XDP_HW_PROG_ID, XDP_FLAGS_HW_MODE);
> if (err)
> goto err_cancel;
>
> --
> 2.20.1
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