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Message-ID: <E5650E49-81B5-4F36-B931-E433A0BD210D@flugsvamp.com>
Date: Sat, 01 Jun 2019 11:12:25 -0700
From: "Jonathan Lemon" <jlemon@...gsvamp.com>
To: "Björn Töpel" <bjorn.topel@...il.com>
Cc: toke@...hat.com, ast@...nel.org, daniel@...earbox.net,
netdev@...r.kernel.org,
"Björn Töpel" <bjorn.topel@...el.com>,
magnus.karlsson@...el.com, brouer@...hat.com, bpf@...r.kernel.org,
jakub.kicinski@...ronome.com, saeedm@...lanox.com
Subject: Re: [PATCH bpf-next v2 1/2] net: xdp: refactor XDP_QUERY_PROG{,_HW}
to netdev
On 31 May 2019, at 2:42, Björn Töpel wrote:
> 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 two new members: xdp_prog_hw and
> xdp_flags. The former is the offloaded XDP program, if any, and the
> latter tracks the flags that the supplied when attaching the XDP
> program. The flags only apply to SKB_MODE or DRV_MODE, not HW_MODE.
>
> The xdp_prog member, previously only used for SKB_MODE, is shared with
> DRV_MODE. This is OK, due to the fact that SKB_MODE and DRV_MODE are
> mutually exclusive. To differentiate between the two modes, a new
> internal flag is introduced as well.
I'm not entirely clear why this new flag is needed - GENERIC seems to
be an alias for SKB_MODE, so why just use SKB_MODE directly?
If the user does not explicitly specify a type (skb|drv|hw), then the
command should choose the correct type and then behave as if this type
was specified.
The logic in dev_change_xdp_fd() is too complicated. It disallows
setting (drv|skb), but allows (hw|skb), which I'm not sure is
intentional.
It should be clearer as to which combinations are allowed.
--
Jonathan
>
> 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. Now that xdp_prog member is shared from a query
> program perspective, 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.
>
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
> ---
> include/linux/netdevice.h | 15 +++--
> include/net/xdp.h | 4 ++
> net/core/dev.c | 138
> ++++++++++++++++++++++++--------------
> net/core/rtnetlink.c | 53 +++++++--------
> net/core/xdp.c | 17 +++--
> 5 files changed, 139 insertions(+), 88 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 44b47e9df94a..f3a875a52c6c 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1940,6 +1940,9 @@ struct net_device {
> #endif
> struct hlist_node index_hlist;
>
> + struct bpf_prog *xdp_prog_hw;
> + u32 xdp_flags;
> +
> /*
> * Cache lines mostly used on transmit path
> */
> @@ -2043,11 +2046,14 @@ struct net_device {
> };
> #define to_net_dev(d) container_of(d, struct net_device, dev)
>
> +/* Reusing the XDP flags space for kernel internal flag */
> +#define XDP_FLAGS_KERN_GENERIC (1U << 4)
> +static_assert(!(XDP_FLAGS_KERN_GENERIC & XDP_FLAGS_MASK));
> +
> 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_KERN_GENERIC;
> }
>
> #define NETDEV_ALIGN 32
> @@ -3684,8 +3690,7 @@ 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 mode);
> 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/include/net/xdp.h b/include/net/xdp.h
> index 0f25b3675c5c..3691280c8fc1 100644
> --- a/include/net/xdp.h
> +++ b/include/net/xdp.h
> @@ -51,6 +51,7 @@ struct xdp_mem_info {
> };
>
> struct page_pool;
> +struct netlink_ext_ack;
>
> struct zero_copy_allocator {
> void (*free)(struct zero_copy_allocator *zca, unsigned long handle);
> @@ -166,4 +167,7 @@ bool xdp_attachment_flags_ok(struct
> xdp_attachment_info *info,
> void xdp_attachment_setup(struct xdp_attachment_info *info,
> struct netdev_bpf *bpf);
>
> +bool xdp_prog_flags_ok(u32 old_flags, u32 new_flags,
> + struct netlink_ext_ack *extack);
> +
> #endif /* __LINUX_NET_XDP_H__ */
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b6b8505cfb3e..1a9da508149a 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -8005,21 +8005,43 @@ 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)
> +static u32 dev_xdp_query_generic(struct net_device *dev)
> {
> - struct netdev_bpf xdp;
> + struct bpf_prog *prog = rtnl_dereference(dev->xdp_prog);
>
> - if (!bpf_op)
> - return 0;
> + return prog && dev->xdp_flags & XDP_FLAGS_KERN_GENERIC ?
> + prog->aux->id : 0;
> +}
>
> - memset(&xdp, 0, sizeof(xdp));
> - xdp.command = cmd;
> +static u32 dev_xdp_query_drv(struct net_device *dev)
> +{
> + struct bpf_prog *prog = rtnl_dereference(dev->xdp_prog);
> +
> + return prog && !(dev->xdp_flags & XDP_FLAGS_KERN_GENERIC) ?
> + prog->aux->id : 0;
> +}
> +
> +static u32 dev_xdp_current_mode(struct net_device *dev)
> +{
> + struct bpf_prog *prog = rtnl_dereference(dev->xdp_prog);
>
> - /* Query must always succeed. */
> - WARN_ON(bpf_op(dev, &xdp) < 0 && cmd == XDP_QUERY_PROG);
> + if (prog)
> + return dev_xdp_query_generic(dev) ? XDP_FLAGS_SKB_MODE :
> + XDP_FLAGS_DRV_MODE;
return xdp->flags & XDP_FLAGS_MODE;
> + return 0;
> +}
>
> - return xdp.prog_id;
> +u32 dev_xdp_query(struct net_device *dev, unsigned int mode)
> +{
> + switch (mode) {
> + case XDP_FLAGS_DRV_MODE:
> + return dev_xdp_query_drv(dev);
> + case XDP_FLAGS_SKB_MODE:
> + return dev_xdp_query_generic(dev);
> + case XDP_FLAGS_HW_MODE:
> + return dev->xdp_prog_hw ? dev->xdp_prog_hw->aux->id : 0;
> + }
> + return 0;
> }
>
> static int dev_xdp_install(struct net_device *dev, bpf_op_t bpf_op,
> @@ -8027,45 +8049,47 @@ static int dev_xdp_install(struct net_device
> *dev, bpf_op_t bpf_op,
> struct bpf_prog *prog)
> {
> struct netdev_bpf xdp;
> + int err;
>
> memset(&xdp, 0, sizeof(xdp));
> - if (flags & XDP_FLAGS_HW_MODE)
> + if (flags & XDP_FLAGS_HW_MODE) {
> xdp.command = XDP_SETUP_PROG_HW;
> - else
> + xdp.flags = XDP_FLAGS_HW_MODE;
> + } else {
> xdp.command = XDP_SETUP_PROG;
> + xdp.flags = flags;
> + }
> xdp.extack = extack;
> - xdp.flags = flags;
> xdp.prog = prog;
>
> - return bpf_op(dev, &xdp);
> + err = bpf_op(dev, &xdp);
> + if (err)
> + return err;
> +
> + if (flags & XDP_FLAGS_HW_MODE) {
> + dev->xdp_prog_hw = prog;
> + return 0;
> + }
> +
> + rcu_assign_pointer(dev->xdp_prog, prog);
> + dev->xdp_flags = prog ? flags : 0;
> + return 0;
> }
>
> 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));
> + struct bpf_prog *prog = rtnl_dereference(dev->xdp_prog);
> + bpf_op_t bpf_op;
>
> - /* 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,
> + if (prog) {
> + bpf_op = dev_xdp_query_generic(dev) ?
> + generic_xdp_install : dev->netdev_ops->ndo_bpf;
> + WARN_ON(dev_xdp_install(dev, bpf_op, NULL, dev->xdp_flags,
> NULL));
> + }
> + if (dev_xdp_query(dev, XDP_FLAGS_HW_MODE))
> + WARN_ON(dev_xdp_install(dev, dev->netdev_ops->ndo_bpf,
> + NULL, XDP_FLAGS_HW_MODE, NULL));
> }
>
> /**
> @@ -8080,41 +8104,49 @@ 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;
> struct bpf_prog *prog = NULL;
> - bpf_op_t bpf_op, bpf_chk;
> + u32 mode, curr_mode;
> + bpf_op_t bpf_op;
> bool offload;
> int err;
>
> ASSERT_RTNL();
>
> offload = flags & XDP_FLAGS_HW_MODE;
> - query = offload ? XDP_QUERY_PROG_HW : XDP_QUERY_PROG;
> + mode = offload ? XDP_FLAGS_HW_MODE : XDP_FLAGS_DRV_MODE;
>
> - bpf_op = bpf_chk = ops->ndo_bpf;
> + bpf_op = dev->netdev_ops->ndo_bpf;
> if (!bpf_op && (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 (fd >= 0) {
> - if (!offload && __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG)) {
> + if (!bpf_op || flags & XDP_FLAGS_SKB_MODE)
> + mode = XDP_FLAGS_SKB_MODE;
> +
> + curr_mode = dev_xdp_current_mode(dev);
> +
> + if (!offload && curr_mode && (mode ^ curr_mode) &
> + (XDP_FLAGS_DRV_MODE | XDP_FLAGS_SKB_MODE)) {
> + if (fd >= 0) {
> 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)) {
> + return 0;
> + }
> +
> + if (!offload && dev_xdp_query(dev, mode) &&
> + !xdp_prog_flags_ok(dev->xdp_flags, flags, extack))
> + return -EBUSY;
> +
> + if (fd >= 0) {
> + if (flags & XDP_FLAGS_UPDATE_IF_NOEXIST &&
> + dev_xdp_query(dev, mode)) {
> 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, !!bpf_op);
> if (IS_ERR(prog))
> return PTR_ERR(prog);
>
> @@ -8125,6 +8157,10 @@ int dev_change_xdp_fd(struct net_device *dev,
> struct netlink_ext_ack *extack,
> }
> }
>
> + if (mode == XDP_FLAGS_SKB_MODE) {
> + bpf_op = generic_xdp_install;
> + flags |= XDP_FLAGS_KERN_GENERIC;
> + }
> err = dev_xdp_install(dev, bpf_op, 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..5e396fd01d8b 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1360,42 +1360,44 @@ 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)
> +static unsigned int rtnl_xdp_mode_to_flag(u8 tgt_mode)
> {
> - 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);
> + switch (tgt_mode) {
> + case XDP_ATTACHED_DRV:
> + return XDP_FLAGS_DRV_MODE;
> + case XDP_ATTACHED_SKB:
> + return XDP_FLAGS_SKB_MODE;
> + case XDP_ATTACHED_HW:
> + return XDP_FLAGS_HW_MODE;
> + }
> + return 0;
> }
>
> -static u32 rtnl_xdp_prog_hw(struct net_device *dev)
> +static u32 rtnl_xdp_mode_to_attr(u8 tgt_mode)
> {
> - return __dev_xdp_query(dev, dev->netdev_ops->ndo_bpf,
> - XDP_QUERY_PROG_HW);
> + switch (tgt_mode) {
> + case XDP_ATTACHED_DRV:
> + return IFLA_XDP_DRV_PROG_ID;
> + case XDP_ATTACHED_SKB:
> + return IFLA_XDP_SKB_PROG_ID;
> + case XDP_ATTACHED_HW:
> + return IFLA_XDP_HW_PROG_ID;
> + }
> + return 0;
> }
>
> 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))
> + u32 *prog_id, u8 *mode, u8 tgt_mode)
> {
> u32 curr_id;
> int err;
>
> - curr_id = get_prog_id(dev);
> + curr_id = dev_xdp_query(dev, rtnl_xdp_mode_to_flag(tgt_mode));
> if (!curr_id)
> return 0;
>
> *prog_id = curr_id;
> - err = nla_put_u32(skb, attr, curr_id);
> + err = nla_put_u32(skb, rtnl_xdp_mode_to_attr(tgt_mode), curr_id);
> if (err)
> return err;
>
> @@ -1420,16 +1422,13 @@ 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);
> + err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode,
> XDP_ATTACHED_SKB);
> 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);
> + err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode,
> XDP_ATTACHED_DRV);
> 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);
> + err = rtnl_xdp_report_one(skb, dev, &prog_id, &mode,
> XDP_ATTACHED_HW);
> if (err)
> goto err_cancel;
>
> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 4b2b194f4f1f..af92c04a58d8 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -388,16 +388,23 @@ int xdp_attachment_query(struct
> xdp_attachment_info *info,
> }
> EXPORT_SYMBOL_GPL(xdp_attachment_query);
>
> -bool xdp_attachment_flags_ok(struct xdp_attachment_info *info,
> - struct netdev_bpf *bpf)
> +bool xdp_prog_flags_ok(u32 old_flags, u32 new_flags,
> + struct netlink_ext_ack *extack)
> {
> - if (info->prog && (bpf->flags ^ info->flags) & XDP_FLAGS_MODES) {
> - NL_SET_ERR_MSG(bpf->extack,
> - "program loaded with different flags");
> + if ((new_flags ^ old_flags) & XDP_FLAGS_MODES) {
> + NL_SET_ERR_MSG(extack, "program loaded with different flags");
> return false;
> }
> return true;
> }
> +
> +bool xdp_attachment_flags_ok(struct xdp_attachment_info *info,
> + struct netdev_bpf *bpf)
> +{
> + if (info->prog)
> + return xdp_prog_flags_ok(bpf->flags, info->flags, bpf->extack);
> + return true;
> +}
> EXPORT_SYMBOL_GPL(xdp_attachment_flags_ok);
>
> void xdp_attachment_setup(struct xdp_attachment_info *info,
> --
> 2.20.1
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