linux/include/net/xdp.h
Jesper Dangaard Brouer b860a1b964 xdp: Adjust xdp_frame layout to avoid using bitfields
Practical experience (and advice from Alexei) tell us that bitfields in
structs lead to un-optimized assembly code. I've verified this change
does lead to better x86_64 assembly, both via objdump and playing with
code snippets in godbolt.org.

Using scripts/bloat-o-meter shows the code size is reduced with 24
bytes for xdp_convert_buff_to_frame() that gets inlined e.g. in
i40e_xmit_xdp_tx_ring() which were used for microbenchmarking.

Microbenchmarking results do show improvements, but very small and
varying between 0.5 to 2 nanosec improvement per packet.

The member @metasize is changed from u8 to u32. Future users of this
area could split this into two u16 fields. I've also benchmarked with
two u16 fields showing equal performance gains and code size reduction.

The moved member @frame_sz doesn't change sizeof struct due to existing
padding. Like xdp_buff member @frame_sz is placed next to @flags, which
allows compiler to optimize assignment of these.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/r/166393728005.2213882.4162674859542409548.stgit@firesoul
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-09-26 13:28:19 -07:00

413 lines
11 KiB
C

/* SPDX-License-Identifier: GPL-2.0-only */
/* include/net/xdp.h
*
* Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
*/
#ifndef __LINUX_NET_XDP_H__
#define __LINUX_NET_XDP_H__
#include <linux/skbuff.h> /* skb_shared_info */
/**
* DOC: XDP RX-queue information
*
* The XDP RX-queue info (xdp_rxq_info) is associated with the driver
* level RX-ring queues. It is information that is specific to how
* the driver have configured a given RX-ring queue.
*
* Each xdp_buff frame received in the driver carries a (pointer)
* reference to this xdp_rxq_info structure. This provides the XDP
* data-path read-access to RX-info for both kernel and bpf-side
* (limited subset).
*
* For now, direct access is only safe while running in NAPI/softirq
* context. Contents are read-mostly and must not be updated during
* driver NAPI/softirq poll.
*
* The driver usage API is a register and unregister API.
*
* The struct is not directly tied to the XDP prog. A new XDP prog
* can be attached as long as it doesn't change the underlying
* RX-ring. If the RX-ring does change significantly, the NIC driver
* naturally need to stop the RX-ring before purging and reallocating
* memory. In that process the driver MUST call unregister (which
* also applies for driver shutdown and unload). The register API is
* also mandatory during RX-ring setup.
*/
enum xdp_mem_type {
MEM_TYPE_PAGE_SHARED = 0, /* Split-page refcnt based model */
MEM_TYPE_PAGE_ORDER0, /* Orig XDP full page model */
MEM_TYPE_PAGE_POOL,
MEM_TYPE_XSK_BUFF_POOL,
MEM_TYPE_MAX,
};
/* XDP flags for ndo_xdp_xmit */
#define XDP_XMIT_FLUSH (1U << 0) /* doorbell signal consumer */
#define XDP_XMIT_FLAGS_MASK XDP_XMIT_FLUSH
struct xdp_mem_info {
u32 type; /* enum xdp_mem_type, but known size type */
u32 id;
};
struct page_pool;
struct xdp_rxq_info {
struct net_device *dev;
u32 queue_index;
u32 reg_state;
struct xdp_mem_info mem;
unsigned int napi_id;
u32 frag_size;
} ____cacheline_aligned; /* perf critical, avoid false-sharing */
struct xdp_txq_info {
struct net_device *dev;
};
enum xdp_buff_flags {
XDP_FLAGS_HAS_FRAGS = BIT(0), /* non-linear xdp buff */
XDP_FLAGS_FRAGS_PF_MEMALLOC = BIT(1), /* xdp paged memory is under
* pressure
*/
};
struct xdp_buff {
void *data;
void *data_end;
void *data_meta;
void *data_hard_start;
struct xdp_rxq_info *rxq;
struct xdp_txq_info *txq;
u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
u32 flags; /* supported values defined in xdp_buff_flags */
};
static __always_inline bool xdp_buff_has_frags(struct xdp_buff *xdp)
{
return !!(xdp->flags & XDP_FLAGS_HAS_FRAGS);
}
static __always_inline void xdp_buff_set_frags_flag(struct xdp_buff *xdp)
{
xdp->flags |= XDP_FLAGS_HAS_FRAGS;
}
static __always_inline void xdp_buff_clear_frags_flag(struct xdp_buff *xdp)
{
xdp->flags &= ~XDP_FLAGS_HAS_FRAGS;
}
static __always_inline bool xdp_buff_is_frag_pfmemalloc(struct xdp_buff *xdp)
{
return !!(xdp->flags & XDP_FLAGS_FRAGS_PF_MEMALLOC);
}
static __always_inline void xdp_buff_set_frag_pfmemalloc(struct xdp_buff *xdp)
{
xdp->flags |= XDP_FLAGS_FRAGS_PF_MEMALLOC;
}
static __always_inline void
xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
{
xdp->frame_sz = frame_sz;
xdp->rxq = rxq;
xdp->flags = 0;
}
static __always_inline void
xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
int headroom, int data_len, const bool meta_valid)
{
unsigned char *data = hard_start + headroom;
xdp->data_hard_start = hard_start;
xdp->data = data;
xdp->data_end = data + data_len;
xdp->data_meta = meta_valid ? data : data + 1;
}
/* Reserve memory area at end-of data area.
*
* This macro reserves tailroom in the XDP buffer by limiting the
* XDP/BPF data access to data_hard_end. Notice same area (and size)
* is used for XDP_PASS, when constructing the SKB via build_skb().
*/
#define xdp_data_hard_end(xdp) \
((xdp)->data_hard_start + (xdp)->frame_sz - \
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
static inline struct skb_shared_info *
xdp_get_shared_info_from_buff(struct xdp_buff *xdp)
{
return (struct skb_shared_info *)xdp_data_hard_end(xdp);
}
static __always_inline unsigned int xdp_get_buff_len(struct xdp_buff *xdp)
{
unsigned int len = xdp->data_end - xdp->data;
struct skb_shared_info *sinfo;
if (likely(!xdp_buff_has_frags(xdp)))
goto out;
sinfo = xdp_get_shared_info_from_buff(xdp);
len += sinfo->xdp_frags_size;
out:
return len;
}
struct xdp_frame {
void *data;
u16 len;
u16 headroom;
u32 metasize; /* uses lower 8-bits */
/* Lifetime of xdp_rxq_info is limited to NAPI/enqueue time,
* while mem info is valid on remote CPU.
*/
struct xdp_mem_info mem;
struct net_device *dev_rx; /* used by cpumap */
u32 frame_sz;
u32 flags; /* supported values defined in xdp_buff_flags */
};
static __always_inline bool xdp_frame_has_frags(struct xdp_frame *frame)
{
return !!(frame->flags & XDP_FLAGS_HAS_FRAGS);
}
static __always_inline bool xdp_frame_is_frag_pfmemalloc(struct xdp_frame *frame)
{
return !!(frame->flags & XDP_FLAGS_FRAGS_PF_MEMALLOC);
}
#define XDP_BULK_QUEUE_SIZE 16
struct xdp_frame_bulk {
int count;
void *xa;
void *q[XDP_BULK_QUEUE_SIZE];
};
static __always_inline void xdp_frame_bulk_init(struct xdp_frame_bulk *bq)
{
/* bq->count will be zero'ed when bq->xa gets updated */
bq->xa = NULL;
}
static inline struct skb_shared_info *
xdp_get_shared_info_from_frame(struct xdp_frame *frame)
{
void *data_hard_start = frame->data - frame->headroom - sizeof(*frame);
return (struct skb_shared_info *)(data_hard_start + frame->frame_sz -
SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
}
struct xdp_cpumap_stats {
unsigned int redirect;
unsigned int pass;
unsigned int drop;
};
/* Clear kernel pointers in xdp_frame */
static inline void xdp_scrub_frame(struct xdp_frame *frame)
{
frame->data = NULL;
frame->dev_rx = NULL;
}
static inline void
xdp_update_skb_shared_info(struct sk_buff *skb, u8 nr_frags,
unsigned int size, unsigned int truesize,
bool pfmemalloc)
{
skb_shinfo(skb)->nr_frags = nr_frags;
skb->len += size;
skb->data_len += size;
skb->truesize += truesize;
skb->pfmemalloc |= pfmemalloc;
}
/* Avoids inlining WARN macro in fast-path */
void xdp_warn(const char *msg, const char *func, const int line);
#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__)
struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct sk_buff *skb,
struct net_device *dev);
struct sk_buff *xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct net_device *dev);
int xdp_alloc_skb_bulk(void **skbs, int n_skb, gfp_t gfp);
struct xdp_frame *xdpf_clone(struct xdp_frame *xdpf);
static inline
void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp)
{
xdp->data_hard_start = frame->data - frame->headroom - sizeof(*frame);
xdp->data = frame->data;
xdp->data_end = frame->data + frame->len;
xdp->data_meta = frame->data - frame->metasize;
xdp->frame_sz = frame->frame_sz;
xdp->flags = frame->flags;
}
static inline
int xdp_update_frame_from_buff(struct xdp_buff *xdp,
struct xdp_frame *xdp_frame)
{
int metasize, headroom;
/* Assure headroom is available for storing info */
headroom = xdp->data - xdp->data_hard_start;
metasize = xdp->data - xdp->data_meta;
metasize = metasize > 0 ? metasize : 0;
if (unlikely((headroom - metasize) < sizeof(*xdp_frame)))
return -ENOSPC;
/* Catch if driver didn't reserve tailroom for skb_shared_info */
if (unlikely(xdp->data_end > xdp_data_hard_end(xdp))) {
XDP_WARN("Driver BUG: missing reserved tailroom");
return -ENOSPC;
}
xdp_frame->data = xdp->data;
xdp_frame->len = xdp->data_end - xdp->data;
xdp_frame->headroom = headroom - sizeof(*xdp_frame);
xdp_frame->metasize = metasize;
xdp_frame->frame_sz = xdp->frame_sz;
xdp_frame->flags = xdp->flags;
return 0;
}
/* Convert xdp_buff to xdp_frame */
static inline
struct xdp_frame *xdp_convert_buff_to_frame(struct xdp_buff *xdp)
{
struct xdp_frame *xdp_frame;
if (xdp->rxq->mem.type == MEM_TYPE_XSK_BUFF_POOL)
return xdp_convert_zc_to_xdp_frame(xdp);
/* Store info in top of packet */
xdp_frame = xdp->data_hard_start;
if (unlikely(xdp_update_frame_from_buff(xdp, xdp_frame) < 0))
return NULL;
/* rxq only valid until napi_schedule ends, convert to xdp_mem_info */
xdp_frame->mem = xdp->rxq->mem;
return xdp_frame;
}
void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
struct xdp_buff *xdp);
void xdp_return_frame(struct xdp_frame *xdpf);
void xdp_return_frame_rx_napi(struct xdp_frame *xdpf);
void xdp_return_buff(struct xdp_buff *xdp);
void xdp_flush_frame_bulk(struct xdp_frame_bulk *bq);
void xdp_return_frame_bulk(struct xdp_frame *xdpf,
struct xdp_frame_bulk *bq);
/* When sending xdp_frame into the network stack, then there is no
* return point callback, which is needed to release e.g. DMA-mapping
* resources with page_pool. Thus, have explicit function to release
* frame resources.
*/
void __xdp_release_frame(void *data, struct xdp_mem_info *mem);
static inline void xdp_release_frame(struct xdp_frame *xdpf)
{
struct xdp_mem_info *mem = &xdpf->mem;
struct skb_shared_info *sinfo;
int i;
/* Curr only page_pool needs this */
if (mem->type != MEM_TYPE_PAGE_POOL)
return;
if (likely(!xdp_frame_has_frags(xdpf)))
goto out;
sinfo = xdp_get_shared_info_from_frame(xdpf);
for (i = 0; i < sinfo->nr_frags; i++) {
struct page *page = skb_frag_page(&sinfo->frags[i]);
__xdp_release_frame(page_address(page), mem);
}
out:
__xdp_release_frame(xdpf->data, mem);
}
static __always_inline unsigned int xdp_get_frame_len(struct xdp_frame *xdpf)
{
struct skb_shared_info *sinfo;
unsigned int len = xdpf->len;
if (likely(!xdp_frame_has_frags(xdpf)))
goto out;
sinfo = xdp_get_shared_info_from_frame(xdpf);
len += sinfo->xdp_frags_size;
out:
return len;
}
int __xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
struct net_device *dev, u32 queue_index,
unsigned int napi_id, u32 frag_size);
static inline int
xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
struct net_device *dev, u32 queue_index,
unsigned int napi_id)
{
return __xdp_rxq_info_reg(xdp_rxq, dev, queue_index, napi_id, 0);
}
void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq);
void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq);
bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq);
int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
enum xdp_mem_type type, void *allocator);
void xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq);
int xdp_reg_mem_model(struct xdp_mem_info *mem,
enum xdp_mem_type type, void *allocator);
void xdp_unreg_mem_model(struct xdp_mem_info *mem);
/* Drivers not supporting XDP metadata can use this helper, which
* rejects any room expansion for metadata as a result.
*/
static __always_inline void
xdp_set_data_meta_invalid(struct xdp_buff *xdp)
{
xdp->data_meta = xdp->data + 1;
}
static __always_inline bool
xdp_data_meta_unsupported(const struct xdp_buff *xdp)
{
return unlikely(xdp->data_meta > xdp->data);
}
static inline bool xdp_metalen_invalid(unsigned long metalen)
{
return (metalen & (sizeof(__u32) - 1)) || (metalen > 32);
}
struct xdp_attachment_info {
struct bpf_prog *prog;
u32 flags;
};
struct netdev_bpf;
void xdp_attachment_setup(struct xdp_attachment_info *info,
struct netdev_bpf *bpf);
#define DEV_MAP_BULK_SIZE XDP_BULK_QUEUE_SIZE
#endif /* __LINUX_NET_XDP_H__ */