mvneta: introduce XDP multi-buffer support

Introduce xdp_frags_tsize field in skb_shared_info data structure to store xdp_buff/xdp_frame truesize (xdp_frags_tsize will be used in xdp multi-buff support). In order to not increase skb_shared_info size we will use a hole due to skb_shared_info alignment. Introduce xdp_frags_size field in skb_shared_info data structure reusing gso_type field in order to store xdp_buff/xdp_frame paged size. xdp_frags_size will be used in xdp multi-buff support.

Signed-off-by Lorenzo Bianconi <[email protected]>

---
 include/linux/skbuff.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

include/linux/skbuff.h +5 -1

index 6bdb0db3e825..1abeba7ef82e 100644
@@ -522,13 +522,17 @@ struct skb_shared_info {
 	unsigned short	gso_segs;
 	struct sk_buff	*frag_list;
 	struct skb_shared_hwtstamps hwtstamps;
-	unsigned int	gso_type;
+	union {
+		unsigned int	gso_type;
+		unsigned int	xdp_frags_size;
+	};
 	u32		tskey;
 
 	/*
 	 * Warning : all fields before dataref are cleared in __alloc_skb()
 	 */
 	atomic_t	dataref;
+	unsigned int	xdp_frags_tsize;
 
 	/* Intermediate layers must ensure that destructor_arg
 	 * remains valid until skb destructor */

Signature · 1 line

2.31.1

Quoted 8 lines · Lorenzo Bianconi

Introduce xdp_frags_tsize field in skb_shared_info data structure to store xdp_buff/xdp_frame truesize (xdp_frags_tsize will be used in xdp multi-buff support). In order to not increase skb_shared_info size we will use a hole due to skb_shared_info alignment. Introduce xdp_frags_size field in skb_shared_info data structure reusing gso_type field in order to store xdp_buff/xdp_frame paged size. xdp_frags_size will be used in xdp multi-buff support.

Quoted 1 line

Signed-off-by Lorenzo Bianconi <[email protected]>

I assume we can use xdp_frags_tsize for anything else above XDP later? Other than simple question looks OK to me.

Acked-by John Fastabend <[email protected]>

Quoted 30 lines

---
 include/linux/skbuff.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

include/linux/skbuff.h +5 -2

index 6bdb0db3e825..1abeba7ef82e 100644
@@ -522,13 +522,17 @@ struct skb_shared_info {
      unsigned short  gso_segs;
      struct sk_buff  *frag_list;
      struct skb_shared_hwtstamps hwtstamps;
-     unsigned int    gso_type;
+     union {
+             unsigned int    gso_type;
+             unsigned int    xdp_frags_size;
+     };
      u32             tskey;
 
      /*
       * Warning : all fields before dataref are cleared in __alloc_skb()
       */
      atomic_t        dataref;
+     unsigned int    xdp_frags_tsize;
 
      /* Intermediate layers must ensure that destructor_arg
       * remains valid until skb destructor */
--

2.31.1

Introduce flags field in xdp_frame and xdp_buffer data structures to define additional buffer features. At the moment the only supported buffer feature is multi-buffer bit (mb). Multi-buffer bit is used to specify if this is a linear buffer (mb = 0) or a multi-buffer frame (mb = 1). In the latter case the driver is expected to initialize the skb_shared_info structure at the end of the first buffer to link together subsequent buffers belonging to the same frame.

Signed-off-by Lorenzo Bianconi <[email protected]>

---

Update multi-buffer bit (mb) in xdp_buff to notify XDP/eBPF layer and XDP remote drivers if this is a "non-linear" XDP buffer. Access skb_shared_info only if xdp_buff mb is set in order to avoid possible cache-misses.

Signed-off-by Lorenzo Bianconi <[email protected]>

---
 drivers/net/ethernet/marvell/mvneta.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

drivers/net/ethernet/marvell/mvneta.c +0 -0

index 5d1007e1b5c9..9f4858e35566 100644

drivers/net/ethernet/marvell/mvneta.c +11 -5

 	for (i = 0; i < sinfo->nr_frags; i++)
 		page_pool_put_full_page(rxq->page_pool,
 					skb_frag_page(&sinfo->frags[i]), true);
+
+out:
 	page_pool_put_page(rxq->page_pool, virt_to_head_page(xdp->data),
 			   sync_len, true);
 }

@@ -2241,7 +2246,6 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 	int data_len = -MVNETA_MH_SIZE, len;
 	struct net_device *dev = pp->dev;
 	enum dma_data_direction dma_dir;
-	struct skb_shared_info *sinfo;
 
 	if (*size > MVNETA_MAX_RX_BUF_SIZE) {
 		len = MVNETA_MAX_RX_BUF_SIZE;

@@ -2261,11 +2265,9 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 
 	/* Prefetch header */
 	prefetch(data);
+	xdp_buff_clear_mb(xdp);
 	xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
 			 data_len, false);
-
-	sinfo = xdp_get_shared_info_from_buff(xdp);
-	sinfo->nr_frags = 0;
 }
 
 static void

@@ -2299,6 +2301,9 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
 		skb_frag_off_set(frag, pp->rx_offset_correction);
 		skb_frag_size_set(frag, data_len);
 		__skb_frag_set_page(frag, page);
+
+		if (!xdp_buff_is_mb(xdp))
+			xdp_buff_set_mb(xdp);
 	} else {
 		page_pool_put_full_page(rxq->page_pool, page, true);
 	}

@@ -2320,8 +2325,12 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
 		      struct xdp_buff *xdp, u32 desc_status)
 {
 	struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
-	int i, num_frags = sinfo->nr_frags;
 	struct sk_buff *skb;
+	u8 num_frags;
+	int i;
+
+	if (unlikely(xdp_buff_is_mb(xdp)))
+		num_frags = sinfo->nr_frags;
 
 	skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
 	if (!skb)

drivers/net/ethernet/marvell/mvneta.c +1 -0

 	for (i = 0; i < num_frags; i++) {
 		skb_frag_t *frag = &sinfo->frags[i];
 

@@ -2341,6 +2353,7 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
 				skb_frag_size(frag), PAGE_SIZE);
 	}
 
+out:
 	return skb;
 }
 

Signature · 1 line

2.31.1

Quoted 18 lines · Lorenzo Bianconi

Update multi-buffer bit (mb) in xdp_buff to notify XDP/eBPF layer and XDP remote drivers if this is a "non-linear" XDP buffer. Access skb_shared_info only if xdp_buff mb is set in order to avoid possible cache-misses.

Signed-off-by Lorenzo Bianconi <[email protected]>

---
 drivers/net/ethernet/marvell/mvneta.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

drivers/net/ethernet/marvell/mvneta.c +0 -0

index 5d1007e1b5c9..9f4858e35566 100644
@@ -2037,9 +2037,14 @@ mvneta_xdp_put_buff(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
 {
      int i;
 

drivers/net/ethernet/marvell/mvneta.c mvneta_xdp_put_buff(struct mvneta_port *pp, struct mvneta_rx_queue *rxq, · line 2042

Quoted 3 lines

drivers/net/ethernet/marvell/mvneta.c +3 -0

+     if (likely(!xdp_buff_is_mb(xdp)))
+             goto out;
+

Wouldn't nr_frags = 0 in the !xdp_buff_is_mb case? Is the xdp_buff_is_mb check with goto really required?

Quoted 58 lines

drivers/net/ethernet/marvell/mvneta.c +11 -5

      for (i = 0; i < sinfo->nr_frags; i++)
              page_pool_put_full_page(rxq->page_pool,
                                      skb_frag_page(&sinfo->frags[i]), true);
+
+out:
      page_pool_put_page(rxq->page_pool, virt_to_head_page(xdp->data),
                         sync_len, true);
 }

@@ -2241,7 +2246,6 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
      int data_len = -MVNETA_MH_SIZE, len;
      struct net_device *dev = pp->dev;
      enum dma_data_direction dma_dir;
-     struct skb_shared_info *sinfo;
 
      if (*size > MVNETA_MAX_RX_BUF_SIZE) {
              len = MVNETA_MAX_RX_BUF_SIZE;

@@ -2261,11 +2265,9 @@ mvneta_swbm_rx_frame(struct mvneta_port *pp,
 
      /* Prefetch header */
      prefetch(data);
+     xdp_buff_clear_mb(xdp);
      xdp_prepare_buff(xdp, data, pp->rx_offset_correction + MVNETA_MH_SIZE,
                       data_len, false);
-
-     sinfo = xdp_get_shared_info_from_buff(xdp);
-     sinfo->nr_frags = 0;
 }
 
 static void

@@ -2299,6 +2301,9 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
              skb_frag_off_set(frag, pp->rx_offset_correction);
              skb_frag_size_set(frag, data_len);
              __skb_frag_set_page(frag, page);
+
+             if (!xdp_buff_is_mb(xdp))
+                     xdp_buff_set_mb(xdp);
      } else {
              page_pool_put_full_page(rxq->page_pool, page, true);
      }

@@ -2320,8 +2325,12 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
                    struct xdp_buff *xdp, u32 desc_status)
 {
      struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
-     int i, num_frags = sinfo->nr_frags;
      struct sk_buff *skb;
+     u8 num_frags;
+     int i;
+
+     if (unlikely(xdp_buff_is_mb(xdp)))
+             num_frags = sinfo->nr_frags;
 
      skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
      if (!skb)

@@ -2333,6 +2342,9 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
      skb_put(skb, xdp->data_end - xdp->data);
      skb->ip_summed = mvneta_rx_csum(pp, desc_status);
 

drivers/net/ethernet/marvell/mvneta.c mvneta_xdp_put_buff(struct mvneta_port *pp, struct mvneta_rx_queue *rxq, · line 2042

Quoted 3 lines

drivers/net/ethernet/marvell/mvneta.c +3 -0

+     if (likely(!xdp_buff_is_mb(xdp)))
+             goto out;
+

Not that I care much, but couldn't you just init num_frags = 0 and avoid the goto?

Anyways its not my driver so no need to change it if you like it better the way it is. Mostly just checking my understanding.

Quoted 14 lines

drivers/net/ethernet/marvell/mvneta.c +1 -1

      for (i = 0; i < num_frags; i++) {
              skb_frag_t *frag = &sinfo->frags[i];
 

@@ -2341,6 +2353,7 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
                              skb_frag_size(frag), PAGE_SIZE);
      }
 
+out:
      return skb;
 }
 
--

2.31.1

Relying on xdp mb bit, remove skb_shared_info structure allocated on the stack in mvneta_rx_swbm routine and simplify mvneta_swbm_add_rx_fragment accessing skb_shared_info in the xdp_buff structure directly. There is no performance penalty in this approach since mvneta_swbm_add_rx_fragment is run just for multi-buff use-case.

Signed-off-by Lorenzo Bianconi <[email protected]>

---

Introduce xdp_update_skb_shared_info routine to update frags array metadata in skb_shared_info data structure converting to a skb from a xdp_buff or xdp_frame.
According to the current skb_shared_info architecture in xdp_frame/xdp_buff and to the xdp multi-buff support, there is
no need to run skb_add_rx_frag() and reset frags array converting the buffer to a skb since the frag array will be in the same position for xdp_buff/xdp_frame and for the skb, we just need to update memory metadata.
Introduce XDP_FLAGS_PF_MEMALLOC flag in xdp_buff_flags in order to mark the xdp_buff or xdp_frame as under memory-pressure if pages of the frags array are under memory pressure. Doing so we can avoid looping over all fragments in xdp_update_skb_shared_info routine. The driver is expected to set the flag constructing the xdp_buffer using xdp_buff_set_frag_pfmemalloc utility routine.
Rely on xdp_update_skb_shared_info in __xdp_build_skb_from_frame routine converting the multi-buff xdp_frame to a skb after performing a XDP_REDIRECT.

Signed-off-by Lorenzo Bianconi <[email protected]>

Rely on xdp_update_skb_shared_info routine in order to avoid resetting frags array in skb_shared_info structure building the skb in mvneta_swbm_build_skb(). Frags array is expected to be initialized by the receiving driver building the xdp_buff and here we just need to update memory metadata.

Signed-off-by Lorenzo Bianconi <[email protected]>

---

 drivers/net/ethernet/marvell/mvneta.c | 35 +++++++++++++++------------
 1 file changed, 20 insertions(+), 15 deletions(-)

drivers/net/ethernet/marvell/mvneta.c +9 -1

index cbf614d6b993..b996eb49d813 100644
@@ -2304,11 +2304,19 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
 		skb_frag_size_set(frag, data_len);
 		__skb_frag_set_page(frag, page);
 
-		if (!xdp_buff_is_mb(xdp))
+		if (!xdp_buff_is_mb(xdp)) {
+			sinfo->xdp_frags_size = *size;
 			xdp_buff_set_mb(xdp);
+		}
+		if (page_is_pfmemalloc(page))
+			xdp_buff_set_frag_pfmemalloc(xdp);
 	} else {
 		page_pool_put_full_page(rxq->page_pool, page, true);
 	}
+
+	/* last fragment */
+	if (len == *size)
+		sinfo->xdp_frags_tsize = sinfo->nr_frags * PAGE_SIZE;
 	*size -= len;
 }
 

@@ -2316,13 +2324,18 @@ static struct sk_buff *
 mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,

drivers/net/ethernet/marvell/mvneta.c +9 -11

+		struct skb_shared_info *sinfo;
+
+		sinfo = xdp_get_shared_info_from_buff(xdp);
+		truesize = sinfo->xdp_frags_tsize;
+		size = sinfo->xdp_frags_size;
 		num_frags = sinfo->nr_frags;
+	}
 
 	skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
 	if (!skb)

@@ -2334,18 +2347,10 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
 	skb_put(skb, xdp->data_end - xdp->data);
 	skb->ip_summed = mvneta_rx_csum(pp, desc_status);
 
-	if (likely(!xdp_buff_is_mb(xdp)))
-		goto out;
-
-	for (i = 0; i < num_frags; i++) {
-		skb_frag_t *frag = &sinfo->frags[i];
-
-		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
-				skb_frag_page(frag), skb_frag_off(frag),
-				skb_frag_size(frag), PAGE_SIZE);
-	}
+	if (unlikely(xdp_buff_is_mb(xdp)))
+		xdp_update_skb_shared_info(skb, num_frags, size, truesize,
+					   xdp_buff_is_frag_pfmemalloc(xdp));
 
-out:
 	return skb;
 }
 

Signature · 1 line

2.31.1

Quoted 8 lines · Lorenzo Bianconi

Rely on xdp_update_skb_shared_info routine in order to avoid resetting frags array in skb_shared_info structure building the skb in mvneta_swbm_build_skb(). Frags array is expected to be initialized by the receiving driver building the xdp_buff and here we just need to update memory metadata.

Signed-off-by Lorenzo Bianconi <[email protected]>

---

Acked-by John Fastabend <[email protected]>

Quoted 38 lines

 drivers/net/ethernet/marvell/mvneta.c | 35 +++++++++++++++------------
 1 file changed, 20 insertions(+), 15 deletions(-)

drivers/net/ethernet/marvell/mvneta.c +10 -3

index cbf614d6b993..b996eb49d813 100644
@@ -2304,11 +2304,19 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
              skb_frag_size_set(frag, data_len);
              __skb_frag_set_page(frag, page);
 
-             if (!xdp_buff_is_mb(xdp))
+             if (!xdp_buff_is_mb(xdp)) {
+                     sinfo->xdp_frags_size = *size;
                      xdp_buff_set_mb(xdp);
+             }
+             if (page_is_pfmemalloc(page))
+                     xdp_buff_set_frag_pfmemalloc(xdp);
      } else {
              page_pool_put_full_page(rxq->page_pool, page, true);
      }
+
+     /* last fragment */
+     if (len == *size)
+             sinfo->xdp_frags_tsize = sinfo->nr_frags * PAGE_SIZE;
      *size -= len;
 }
 

@@ -2316,13 +2324,18 @@ static struct sk_buff *
 mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
                    struct xdp_buff *xdp, u32 desc_status)
 {
-     struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
+     unsigned int size, truesize;
      struct sk_buff *skb;
      u8 num_frags;
-     int i;
 

drivers/net/ethernet/marvell/mvneta.c static struct sk_buff * · line 2331

Quoted 2 lines

drivers/net/ethernet/marvell/mvneta.c +1 -1

-     if (unlikely(xdp_buff_is_mb(xdp)))
+     if (unlikely(xdp_buff_is_mb(xdp))) {

Just curious does the mvneta hardware support header split? If we get to that point then we can drop the unlikely.

Quoted 36 lines

drivers/net/ethernet/marvell/mvneta.c +9 -12

+             struct skb_shared_info *sinfo;
+
+             sinfo = xdp_get_shared_info_from_buff(xdp);
+             truesize = sinfo->xdp_frags_tsize;
+             size = sinfo->xdp_frags_size;
              num_frags = sinfo->nr_frags;
+     }
 
      skb = build_skb(xdp->data_hard_start, PAGE_SIZE);
      if (!skb)

@@ -2334,18 +2347,10 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
      skb_put(skb, xdp->data_end - xdp->data);
      skb->ip_summed = mvneta_rx_csum(pp, desc_status);
 
-     if (likely(!xdp_buff_is_mb(xdp)))
-             goto out;
-
-     for (i = 0; i < num_frags; i++) {
-             skb_frag_t *frag = &sinfo->frags[i];
-
-             skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
-                             skb_frag_page(frag), skb_frag_off(frag),
-                             skb_frag_size(frag), PAGE_SIZE);
-     }
+     if (unlikely(xdp_buff_is_mb(xdp)))
+             xdp_update_skb_shared_info(skb, num_frags, size, truesize,
+                                        xdp_buff_is_frag_pfmemalloc(xdp));
 
-out:
      return skb;
 }
 
--

2.31.1

Take into account if the received xdp_buff/xdp_frame is non-linear recycling/returning the frame memory to the allocator or into xdp_frame_bulk.

Signed-off-by Lorenzo Bianconi <[email protected]>

---

Introduce the capability to map non-linear xdp buffer running mvneta_xdp_submit_frame() for XDP_TX and XDP_REDIRECT

Signed-off-by Lorenzo Bianconi <[email protected]>

Enable the capability to receive jumbo frames even if the interface is running in XDP mode

Signed-off-by Lorenzo Bianconi <[email protected]>

---

From: Eelco Chaudron <[email protected]>

This change adds support for tail growing and shrinking for XDP multi-buff.

When called on a multi-buffer packet with a grow request, it will always work on the last fragment of the packet. So the maximum grow size is the last fragments tailroom, i.e. no new buffer will be allocated.

When shrinking, it will work from the last fragment, all the way down to the base buffer depending on the shrinking size. It's important to mention that once you shrink down the fragment(s) are freed, so you can not grow again to the original size.

Co-developed-by Lorenzo Bianconi <[email protected]>

Signed-off-by Lorenzo Bianconi <[email protected]>

Signed-off-by Eelco Chaudron <[email protected]>

---

Introduce bpf_xdp_get_buff_len helper in order to return the xdp buffer total size (linear and paged area)

Signed-off-by Lorenzo Bianconi <[email protected]>

---

From: Eelco Chaudron <[email protected]>

This patch adds support for multi-buffer for the following helpers:
- bpf_xdp_output()
- bpf_perf_event_output()

Signed-off-by Eelco Chaudron <[email protected]>

Signed-off-by Lorenzo Bianconi <[email protected]>

---

For XDP frames split over multiple buffers, the xdp_md->data and xdp_md->data_end pointers will point to the start and end of the first fragment only. bpf_xdp_adjust_data can be used to access subsequent fragments by moving the data pointers. To use, an XDP program can call this helper with the byte offset of the packet payload that
it wants to access; the helper will move xdp_md->data and xdp_md ->data_end so they point to the requested payload offset and to the end of the fragment containing this byte offset, and return the byte offset of the

start of the fragment.
To move back to the beginning of the packet, simply call the helper with an offset of '0'.
Note also that the helpers that modify the packet boundaries (bpf_xdp_adjust_head(), bpf_xdp_adjust_tail() and bpf_xdp_adjust_meta()) will fail if the pointers have been moved; it is the responsibility of the BPF program to move them back before using these helpers.

Suggested-by John Fastabend <[email protected]>

Signed-off-by Lorenzo Bianconi <[email protected]>

---
 include/net/xdp.h              |  8 +++++
 include/uapi/linux/bpf.h       | 32 ++++++++++++++++++
 net/bpf/test_run.c             |  8 +++++
 net/core/filter.c              | 62 +++++++++++++++++++++++++++++++++-
 tools/include/uapi/linux/bpf.h | 32 ++++++++++++++++++
 5 files changed, 141 insertions(+), 1 deletion(-)

include/net/xdp.h +8 -0

index cdaecf8d4d61..ce4764c7cd40 100644
@@ -82,6 +82,11 @@ struct xdp_buff {
 	struct xdp_txq_info *txq;
 	u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
 	u16 flags; /* supported values defined in xdp_flags */
+	/* xdp multi-buff metadata used for frags iteration */
+	struct {
+		u16 headroom;	/* frame headroom: data - data_hard_start */
+		u16 headlen;	/* first buffer length: data_end - data */
+	} mb;
 };
 
 static __always_inline bool xdp_buff_is_mb(struct xdp_buff *xdp)

@@ -127,6 +132,9 @@ xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
 	xdp->data = data;
 	xdp->data_end = data + data_len;
 	xdp->data_meta = meta_valid ? data : data + 1;
+	/* mb metadata for frags iteration */
+	xdp->mb.headroom = headroom;
+	xdp->mb.headlen = data_len;
 }
 
 /* Reserve memory area at end-of data area.

include/uapi/linux/bpf.h +0 -0

index 9e2c3b12ea49..a7b5185a718a 100644

include/uapi/linux/bpf.h +27 -0

+ *		will point to the start and end of the first fragment only.
+ *		This helper can be used to access subsequent fragments by
+ *		moving the data pointers. To use, an XDP program can call
+ *		this helper with the byte offset of the packet payload that
+ *		it wants to access; the helper will move *xdp_md*\ **->data**
+ *		and *xdp_md *\ **->data_end** so they point to the requested
+ *		payload offset and to the end of the fragment containing this
+ *		byte offset, and return the byte offset of the start of the
+ *		fragment.
+ *		To move back to the beginning of the packet, simply call the
+ *		helper with an offset of '0'.
+ *		Note also that the helpers that modify the packet boundaries
+ *		(*bpf_xdp_adjust_head()*, *bpf_xdp_adjust_tail()* and
+ *		*bpf_xdp_adjust_meta()*) will fail if the pointers have been
+ *		moved; it is the responsibility of the BPF program to move them
+ *		back before using these helpers.
+ *
+ *		A call to this helper is susceptible to change the underlying
+ *		packet buffer. Therefore, at load time, all checks on pointers
+ *		previously done by the verifier are invalidated and must be
+ *		performed again, if the helper is used in combination with
+ *		direct packet access.
+ *	Return
+ *		offset between the beginning of the current fragment and
+ *		original *xdp_md*\ **->data** on success, or a negative error
+ *		in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\

@@ -5055,6 +5086,7 @@ union bpf_attr {
 	FN(get_func_ip),		\
 	FN(get_attach_cookie),		\
 	FN(xdp_get_buff_len),		\
+	FN(xdp_adjust_data),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper

net/bpf/test_run.c +8 -0

index 869dcf23a1ca..f09c2c8c0d6c 100644
@@ -757,6 +757,8 @@ static int xdp_convert_md_to_buff(struct xdp_md *xdp_md, struct xdp_buff *xdp)
 	}
 
 	xdp->data = xdp->data_meta + xdp_md->data;
+	xdp->mb.headroom = xdp->data - xdp->data_hard_start;
+	xdp->mb.headlen = xdp->data_end - xdp->data;
 	return 0;
 
 free_dev:

@@ -871,6 +873,12 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 	if (ret)
 		goto out;
 
+	/* data pointers need to be reset after frag iteration */
+	if (unlikely(xdp.data_hard_start + xdp.mb.headroom != xdp.data)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
 	size = xdp.data_end - xdp.data_meta + sinfo->xdp_frags_size;
 	ret = bpf_test_finish(kattr, uattr, xdp.data_meta, sinfo, size,
 			      retval, duration);

net/core/filter.c +0 -0

index 2122c00c680f..ed2a6632adce 100644

net/core/filter.c +4 -0

+
 	if (unlikely(data < data_start ||
 		     data > xdp->data_end - ETH_HLEN))
 		return -EINVAL;

@@ -3836,6 +3840,9 @@ BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
 			xdp->data_meta, metalen);
 	xdp->data_meta += offset;
 	xdp->data = data;
+	/* update metada for multi-buff frag iteration */
+	xdp->mb.headroom = xdp->data - xdp->data_hard_start;
+	xdp->mb.headlen = xdp->data_end - xdp->data;
 
 	return 0;
 }

net/core/filter.c +0 -0

 	if (xdp_data_meta_unsupported(xdp))
 		return -ENOTSUPP;
 	if (unlikely(meta < xdp_frame_end ||

@@ -3970,6 +3985,48 @@ static const struct bpf_func_proto bpf_xdp_adjust_meta_proto = {
 	.arg2_type	= ARG_ANYTHING,

net/core/filter.c +25 -0

+
+	if (offset < xdp->mb.headlen) {
+		/* linear area */
+		xdp->data = xdp->data_hard_start + xdp->mb.headroom + offset;
+		xdp->data_end = xdp->data_hard_start + xdp->mb.headroom +
+				xdp->mb.headlen;
+		return 0;
+	}
+
+	for (i = 0; i < sinfo->nr_frags; i++) {
+		/* paged area */
+		skb_frag_t *frag = &sinfo->frags[i];
+		unsigned int size = skb_frag_size(frag);
+
+		if (offset < base_offset + size) {
+			u8 *addr = skb_frag_address(frag);
+
+			xdp->data = addr + offset - base_offset;
+			xdp->data_end = addr + size;
+			break;
+		}
+		base_offset += size;
+	}
+	return base_offset;
+}

Quoted 8 lines · Lorenzo Bianconi

For XDP frames split over multiple buffers, the xdp_md->data and xdp_md->data_end pointers will point to the start and end of the first fragment only. bpf_xdp_adjust_data can be used to access subsequent fragments by moving the data pointers. To use, an XDP program can call this helper with the byte offset of the packet payload that
it wants to access; the helper will move xdp_md->data and xdp_md ->data_end so they point to the requested payload offset and to the end of the fragment containing this byte offset, and return the byte offset of the

Quoted 8 lines

start of the fragment.
To move back to the beginning of the packet, simply call the helper with an offset of '0'.
Note also that the helpers that modify the packet boundaries (bpf_xdp_adjust_head(), bpf_xdp_adjust_tail() and bpf_xdp_adjust_meta()) will fail if the pointers have been moved; it is the responsibility of the BPF program to move them back before using these helpers.

I'm ok with this for a first iteration I guess with more work we can make the helpers use the updated pointers though.

Quoted 3 lines

Suggested-by John Fastabend <[email protected]>

Signed-off-by Lorenzo Bianconi <[email protected]>

Overall looks good couple small nits/questions below. Thanks!

Quoted 39 lines

---
 include/net/xdp.h              |  8 +++++
 include/uapi/linux/bpf.h       | 32 ++++++++++++++++++
 net/bpf/test_run.c             |  8 +++++
 net/core/filter.c              | 62 +++++++++++++++++++++++++++++++++-
 tools/include/uapi/linux/bpf.h | 32 ++++++++++++++++++
 5 files changed, 141 insertions(+), 1 deletion(-)

include/net/xdp.h +8 -0

index cdaecf8d4d61..ce4764c7cd40 100644
@@ -82,6 +82,11 @@ struct xdp_buff {
      struct xdp_txq_info *txq;
      u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
      u16 flags; /* supported values defined in xdp_flags */
+     /* xdp multi-buff metadata used for frags iteration */
+     struct {
+             u16 headroom;   /* frame headroom: data - data_hard_start */
+             u16 headlen;    /* first buffer length: data_end - data */
+     } mb;
 };
 
 static __always_inline bool xdp_buff_is_mb(struct xdp_buff *xdp)

@@ -127,6 +132,9 @@ xdp_prepare_buff(struct xdp_buff *xdp, unsigned char *hard_start,
      xdp->data = data;
      xdp->data_end = data + data_len;
      xdp->data_meta = meta_valid ? data : data + 1;
+     /* mb metadata for frags iteration */
+     xdp->mb.headroom = headroom;
+     xdp->mb.headlen = data_len;
 }
 
 /* Reserve memory area at end-of data area.

include/uapi/linux/bpf.h +0 -0

index 9e2c3b12ea49..a7b5185a718a 100644

include/uapi/linux/bpf.h union bpf_attr { · line 4884

Quoted 8 lines

include/uapi/linux/bpf.h +5 -0

@@ -4877,6 +4877,37 @@ union bpf_attr {
  *           Get the total size of a given xdp buff (linear and paged area)
  *   Return
  *           The total size of a given xdp buffer.
+ *
+ * long bpf_xdp_adjust_data(struct xdp_buff *xdp_md, u32 offset)
+ *   Description
+ *           For XDP frames split over multiple buffers, the
+ *           *xdp_md*\ **->data** and*xdp_md *\ **->data_end** pointers

                                       ^^^^

missing space?

Quoted 72 lines

include/uapi/linux/bpf.h +27 -0

+ *           will point to the start and end of the first fragment only.
+ *           This helper can be used to access subsequent fragments by
+ *           moving the data pointers. To use, an XDP program can call
+ *           this helper with the byte offset of the packet payload that
+ *           it wants to access; the helper will move *xdp_md*\ **->data**
+ *           and *xdp_md *\ **->data_end** so they point to the requested
+ *           payload offset and to the end of the fragment containing this
+ *           byte offset, and return the byte offset of the start of the
+ *           fragment.
+ *           To move back to the beginning of the packet, simply call the
+ *           helper with an offset of '0'.
+ *           Note also that the helpers that modify the packet boundaries
+ *           (*bpf_xdp_adjust_head()*, *bpf_xdp_adjust_tail()* and
+ *           *bpf_xdp_adjust_meta()*) will fail if the pointers have been
+ *           moved; it is the responsibility of the BPF program to move them
+ *           back before using these helpers.
+ *
+ *           A call to this helper is susceptible to change the underlying
+ *           packet buffer. Therefore, at load time, all checks on pointers
+ *           previously done by the verifier are invalidated and must be
+ *           performed again, if the helper is used in combination with
+ *           direct packet access.
+ *   Return
+ *           offset between the beginning of the current fragment and
+ *           original *xdp_md*\ **->data** on success, or a negative error
+ *           in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)                \
      FN(unspec),                     \

@@ -5055,6 +5086,7 @@ union bpf_attr {
      FN(get_func_ip),                \
      FN(get_attach_cookie),          \
      FN(xdp_get_buff_len),           \
+     FN(xdp_adjust_data),            \
      /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper

net/bpf/test_run.c +8 -0

index 869dcf23a1ca..f09c2c8c0d6c 100644
@@ -757,6 +757,8 @@ static int xdp_convert_md_to_buff(struct xdp_md *xdp_md, struct xdp_buff *xdp)
      }
 
      xdp->data = xdp->data_meta + xdp_md->data;
+     xdp->mb.headroom = xdp->data - xdp->data_hard_start;
+     xdp->mb.headlen = xdp->data_end - xdp->data;
      return 0;
 
 free_dev:

@@ -871,6 +873,12 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
      if (ret)
              goto out;
 
+     /* data pointers need to be reset after frag iteration */
+     if (unlikely(xdp.data_hard_start + xdp.mb.headroom != xdp.data)) {
+             ret = -EFAULT;
+             goto out;
+     }
+
      size = xdp.data_end - xdp.data_meta + sinfo->xdp_frags_size;
      ret = bpf_test_finish(kattr, uattr, xdp.data_meta, sinfo, size,
                            retval, duration);

net/core/filter.c +0 -0

index 2122c00c680f..ed2a6632adce 100644
@@ -3827,6 +3827,10 @@ BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
      void *data_start = xdp_frame_end + metalen;
      void *data = xdp->data + offset;
 

net/core/filter.c BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset) · line 3832

Quoted 3 lines

net/core/filter.c +3 -0

+     /* data pointers need to be reset after frag iteration */
+     if (unlikely(xdp->data_hard_start + xdp->mb.headroom != xdp->data))
+             return -EINVAL;

-EFAULT? It might be nice if error code is different from below for debugging?

Quoted 19 lines

net/core/filter.c +4 -0

+
      if (unlikely(data < data_start ||
                   data > xdp->data_end - ETH_HLEN))
              return -EINVAL;

@@ -3836,6 +3840,9 @@ BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
                      xdp->data_meta, metalen);
      xdp->data_meta += offset;
      xdp->data = data;
+     /* update metada for multi-buff frag iteration */
+     xdp->mb.headroom = xdp->data - xdp->data_hard_start;
+     xdp->mb.headlen = xdp->data_end - xdp->data;
 
      return 0;
 }

@@ -3910,6 +3917,10 @@ BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
      void *data_hard_end = xdp_data_hard_end(xdp); /* use xdp->frame_sz */
      void *data_end = xdp->data_end + offset;
 

net/core/filter.c BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) · line 3922

Quoted 3 lines

net/core/filter.c +3 -0

+     /* data pointer needs to be reset after frag iteration */
+     if (unlikely(xdp->data + xdp->mb.headlen != xdp->data_end))
+             return -EINVAL;

EFAULT?

Quoted 9 lines

net/core/filter.c +1 -0

+
      if (unlikely(xdp_buff_is_mb(xdp)))
              return bpf_xdp_mb_adjust_tail(xdp, offset);
 

@@ -3949,6 +3960,10 @@ BPF_CALL_2(bpf_xdp_adjust_meta, struct xdp_buff *, xdp, int, offset)
      void *meta = xdp->data_meta + offset;
      unsigned long metalen = xdp->data - meta;
 

net/core/filter.c BPF_CALL_2(bpf_xdp_adjust_meta, struct xdp_buff *, xdp, int, offset) · line 3965

Quoted 3 lines

net/core/filter.c +3 -0

+     /* data pointer needs to be reset after frag iteration */
+     if (unlikely(xdp->data_hard_start + xdp->mb.headroom != xdp->data))
+             return -EINVAL;

same comment.

Quoted 8 lines

net/core/filter.c +0 -0

      if (xdp_data_meta_unsupported(xdp))
              return -ENOTSUPP;
      if (unlikely(meta < xdp_frame_end ||

@@ -3970,6 +3985,48 @@ static const struct bpf_func_proto bpf_xdp_adjust_meta_proto = {
      .arg2_type      = ARG_ANYTHING,
 };
 

net/core/filter.c static const struct bpf_func_proto bpf_xdp_adjust_meta_proto = { · line 3995

Quoted 8 lines

net/core/filter.c +8 -0

+BPF_CALL_2(bpf_xdp_adjust_data, struct xdp_buff *, xdp, u32, offset)
+{
+     struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
+     u32 base_offset = xdp->mb.headlen;
+     int i;
+
+     if (!xdp_buff_is_mb(xdp) || offset > sinfo->xdp_frags_size)
+             return -EINVAL;

Do we need to error this? If its not mb we can just return the same as offset==0?

Quoted 26 lines

net/core/filter.c +25 -0

+
+     if (offset < xdp->mb.headlen) {
+             /* linear area */
+             xdp->data = xdp->data_hard_start + xdp->mb.headroom + offset;
+             xdp->data_end = xdp->data_hard_start + xdp->mb.headroom +
+                             xdp->mb.headlen;
+             return 0;
+     }
+
+     for (i = 0; i < sinfo->nr_frags; i++) {
+             /* paged area */
+             skb_frag_t *frag = &sinfo->frags[i];
+             unsigned int size = skb_frag_size(frag);
+
+             if (offset < base_offset + size) {
+                     u8 *addr = skb_frag_address(frag);
+
+                     xdp->data = addr + offset - base_offset;
+                     xdp->data_end = addr + size;
+                     break;
+             }
+             base_offset += size;
+     }
+     return base_offset;
+}

This series introduce XDP multi-buffer support. The mvneta driver is the first to support these new "non-linear" xdp_{buff,frame}. Reviewers please focus on how these new types of xdp_{buff,frame} packets traverse the different layers and the layout design. It is on purpose that BPF-helpers are kept simple, as we don't want to expose the internal layout to allow later changes.

The main idea for the new multi-buffer layout is to reuse the same structure used for non-linear SKB. This rely on the "skb_shared_info" struct at the end of the first buffer to link together subsequent buffers. Keeping the layout compatible with SKBs is also done to ease and speedup creating a SKB from an xdp_{buff,frame}. Converting xdp_frame to SKB and deliver it to the network stack is shown in patch 05/18 (e.g. cpumaps).

A multi-buffer bit (mb) has been introduced in the flags field of xdp_{buff,frame} structure to notify the bpf/network layer if this is a xdp multi-buffer frame (mb = 1) or not (mb = 0).
The mb bit will be set by a xdp multi-buffer capable driver only for non-linear frames maintaining the capability to receive linear frames without any extra cost since the skb_shared_info structure at the end of the first buffer will be initialized only if mb is set.
Moreover the flags field in xdp_{buff,frame} will be reused even for xdp rx csum offloading in future series.

Typical use cases for this series are:
- Jumbo-frames
- Packet header split (please see Google���s use-case @ NetDevConf 0x14, [0])
- TSO/GRO

The two following ebpf helpers (and related selftests) has been introduced:
- bpf_xdp_adjust_data:
Move xdp_md->data and xdp_md->data_end pointers in subsequent fragments according to the offset provided by the ebpf program. This helper can be used to read/write values in frame payload.
- bpf_xdp_get_buff_len:
Return the total frame size (linear + paged parts)

bpf_xdp_adjust_tail and bpf_xdp_copy helpers have been modified to take into account xdp multi-buff frames.

More info about the main idea behind this approach can be found here [1][2].

Changes since v11:
- add missing static to bpf_xdp_get_buff_len_proto structure
- fix bpf_xdp_adjust_data helper when offset is smaller than linear area length.

Changes since v10:
- move xdp->data to the requested payload offset instead of to the beginning of the fragment in bpf_xdp_adjust_data()

Changes since v9:
- introduce bpf_xdp_adjust_data helper and related selftest
- add xdp_frags_size and xdp_frags_tsize fields in skb_shared_info
- introduce xdp_update_skb_shared_info utility routine in ordere to not reset frags array in skb_shared_info converting from a xdp_buff/xdp_frame to a skb
- simplify bpf_xdp_copy routine

Changes since v8:
- add proper dma unmapping if XDP_TX fails on mvneta for a xdp multi-buff
- switch back to skb_shared_info implementation from previous xdp_shared_info one
- avoid using a bietfield in xdp_buff/xdp_frame since it introduces performance regressions. Tested now on 10G NIC (ixgbe) to verify there are no performance penalties for regular codebase
- add bpf_xdp_get_buff_len helper and remove frame_length field in xdp ctx
- add data_len field in skb_shared_info struct
- introduce XDP_FLAGS_FRAGS_PF_MEMALLOC flag

Changes since v7:
- rebase on top of bpf-next
- fix sparse warnings
- improve comments for frame_length in include/net/xdp.h

Changes since v6:
- the main difference respect to previous versions is the new approach proposed by Eelco to pass full length of the packet to eBPF layer in XDP context
- reintroduce multi-buff support to eBPF kself-tests
- reintroduce multi-buff support to bpf_xdp_adjust_tail helper
- introduce multi-buffer support to bpf_xdp_copy helper
- rebase on top of bpf-next

Changes since v5:
- rebase on top of bpf-next
- initialize mb bit in xdp_init_buff() and drop per-driver initialization
- drop xdp->mb initialization in xdp_convert_zc_to_xdp_frame()
- postpone introduction of frame_length field in XDP ctx to another series
- minor changes

Changes since v4:
- rebase ontop of bpf-next
- introduce xdp_shared_info to build xdp multi-buff instead of using the skb_shared_info struct
- introduce frame_length in xdp ctx
- drop previous bpf helpers
- fix bpf_xdp_adjust_tail for xdp multi-buff
- introduce xdp multi-buff self-tests for bpf_xdp_adjust_tail
- fix xdp_return_frame_bulk for xdp multi-buff

Changes since v3:
- rebase ontop of bpf-next
- add patch 10/13 to copy back paged data from a xdp multi-buff frame to userspace buffer for xdp multi-buff selftests

Changes since v2:
- add throughput measurements
- drop bpf_xdp_adjust_mb_header bpf helper
- introduce selftest for xdp multibuffer
- addressed comments on bpf_xdp_get_frags_count
- introduce xdp multi-buff support to cpumaps

Changes since v1:
- Fix use-after-free in xdp_return_{buff/frame}
- Introduce bpf helpers
- Introduce xdp_mb sample program
- access skb_shared_info->nr_frags only on the last fragment

Changes since RFC:
- squash multi-buffer bit initialization in a single patch
- add mvneta non-linear XDP buff support for tx side

[0] https://netdevconf.info/0x14/session.html?talk-the-path-to-tcp-4k-mtu-and-rx-zerocopy
[1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
[2] https://netdevconf.info/0x14/session.html?tutorial-add-XDP-support-to-a-NIC-driver (XDPmulti-buffers section)

Eelco Chaudron (3):
bpf: add multi-buff support to the bpf_xdp_adjust_tail() API
bpf: add multi-buffer support to xdp copy helpers
bpf: update xdp_adjust_tail selftest to include multi-buffer

Lorenzo Bianconi (15):
net: skbuff: add size metadata to skb_shared_info for xdp
xdp: introduce flags field in xdp_buff/xdp_frame
net: mvneta: update mb bit before passing the xdp buffer to eBPF layer
net: mvneta: simplify mvneta_swbm_add_rx_fragment management
net: xdp: add xdp_update_skb_shared_info utility routine
net: marvell: rely on xdp_update_skb_shared_info utility routine
xdp: add multi-buff support to xdp_return_{buff/frame}
net: mvneta: add multi buffer support to XDP_TX
net: mvneta: enable jumbo frames for XDP
bpf: introduce bpf_xdp_get_buff_len helper
bpf: move user_size out of bpf_test_init
bpf: introduce multibuff support to bpf_prog_test_run_xdp()
bpf: test_run: add xdp_shared_info pointer in bpf_test_finish
signature
net: xdp: introduce bpf_xdp_adjust_data helper
bpf: add bpf_xdp_adjust_data selftest

 drivers/net/ethernet/marvell/mvneta.c         | 204 ++++++++++-------
 include/linux/skbuff.h                        |   6 +-
 include/net/xdp.h                             |  95 +++++++-
 include/uapi/linux/bpf.h                      |  39 ++++
 kernel/trace/bpf_trace.c                      |   3 +
 net/bpf/test_run.c                            | 117 ++++++++--
 net/core/filter.c                             | 213 +++++++++++++++++-
 net/core/xdp.c                                |  76 ++++++-
 tools/include/uapi/linux/bpf.h                |  39 ++++
 .../bpf/prog_tests/xdp_adjust_data.c          |  55 +++++
 .../bpf/prog_tests/xdp_adjust_tail.c          | 118 ++++++++++
 .../selftests/bpf/prog_tests/xdp_bpf2bpf.c    | 151 +++++++++----
 .../bpf/progs/test_xdp_adjust_tail_grow.c     |  10 +-
 .../bpf/progs/test_xdp_adjust_tail_shrink.c   |  32 ++-
 .../selftests/bpf/progs/test_xdp_bpf2bpf.c    |   2 +-
 .../bpf/progs/test_xdp_update_frags.c         |  41 ++++
 16 files changed, 1036 insertions(+), 165 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_adjust_data.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_update_frags.c

Signature · 1 line

2.31.1

Quoted 15 lines · Lorenzo Bianconi

This series introduce XDP multi-buffer support. The mvneta driver is the first to support these new "non-linear" xdp_{buff,frame}. Reviewers please focus on how these new types of xdp_{buff,frame} packets traverse the different layers and the layout design. It is on purpose that BPF-helpers are kept simple, as we don't want to expose the internal layout to allow later changes.

The main idea for the new multi-buffer layout is to reuse the same structure used for non-linear SKB. This rely on the "skb_shared_info" struct at the end of the first buffer to link together subsequent buffers. Keeping the layout compatible with SKBs is also done to ease and speedup creating a SKB from an xdp_{buff,frame}. Converting xdp_frame to SKB and deliver it to the network stack is shown in patch 05/18 (e.g. cpumaps).

Quoted 10 lines

A multi-buffer bit (mb) has been introduced in the flags field of xdp_{buff,frame} structure to notify the bpf/network layer if this is a xdp multi-buffer frame (mb = 1) or not (mb = 0).
The mb bit will be set by a xdp multi-buffer capable driver only for non-linear frames maintaining the capability to receive linear frames without any extra cost since the skb_shared_info structure at the end of the first buffer will be initialized only if mb is set.
Moreover the flags field in xdp_{buff,frame} will be reused even for xdp rx csum offloading in future series.

The series is looking really close to me. Couple small comments/questions inline. Also I think we should call out the potential issues in the cover letter with regards to backwards compatibility. Something like,

"
A multi-buffer enabled NIC may receive XDP frames with multiple frags. If a BPF program does not understand mb layouts its possible to contrive a BPF program that incorrectly views data_end as the end of data when there is more data in the payload. Note helpers will generally due the correct thing, for example perf_output will consume entire payload. But, it is still possible some programs could do the wrong thing even if in an edge case. Although we expect most BPF programs not to be impacted we can't rule out, you've been warned.

"

I can't think of an elegant way around this and it does require at least some type of opt-in by increasing the MTU limit so I'm OK with it given I think it should impact few (no?) real programs.

Quoted 146 lines

Typical use cases for this series are:
- Jumbo-frames
- Packet header split (please see Google���s use-case @ NetDevConf 0x14, [0])
- TSO/GRO

The two following ebpf helpers (and related selftests) has been introduced:
- bpf_xdp_adjust_data:
Move xdp_md->data and xdp_md->data_end pointers in subsequent fragments according to the offset provided by the ebpf program. This helper can be used to read/write values in frame payload.
- bpf_xdp_get_buff_len:
Return the total frame size (linear + paged parts)

bpf_xdp_adjust_tail and bpf_xdp_copy helpers have been modified to take into account xdp multi-buff frames.

More info about the main idea behind this approach can be found here [1][2].

Changes since v11:
- add missing static to bpf_xdp_get_buff_len_proto structure
- fix bpf_xdp_adjust_data helper when offset is smaller than linear area length.

Changes since v10:
- move xdp->data to the requested payload offset instead of to the beginning of the fragment in bpf_xdp_adjust_data()

Changes since v9:
- introduce bpf_xdp_adjust_data helper and related selftest
- add xdp_frags_size and xdp_frags_tsize fields in skb_shared_info
- introduce xdp_update_skb_shared_info utility routine in ordere to not reset frags array in skb_shared_info converting from a xdp_buff/xdp_frame to a skb
- simplify bpf_xdp_copy routine

Changes since v8:
- add proper dma unmapping if XDP_TX fails on mvneta for a xdp multi-buff
- switch back to skb_shared_info implementation from previous xdp_shared_info one
- avoid using a bietfield in xdp_buff/xdp_frame since it introduces performance regressions. Tested now on 10G NIC (ixgbe) to verify there are no performance penalties for regular codebase
- add bpf_xdp_get_buff_len helper and remove frame_length field in xdp ctx
- add data_len field in skb_shared_info struct
- introduce XDP_FLAGS_FRAGS_PF_MEMALLOC flag

Changes since v7:
- rebase on top of bpf-next
- fix sparse warnings
- improve comments for frame_length in include/net/xdp.h

Changes since v6:
- the main difference respect to previous versions is the new approach proposed by Eelco to pass full length of the packet to eBPF layer in XDP context
- reintroduce multi-buff support to eBPF kself-tests
- reintroduce multi-buff support to bpf_xdp_adjust_tail helper
- introduce multi-buffer support to bpf_xdp_copy helper
- rebase on top of bpf-next

Changes since v5:
- rebase on top of bpf-next
- initialize mb bit in xdp_init_buff() and drop per-driver initialization
- drop xdp->mb initialization in xdp_convert_zc_to_xdp_frame()
- postpone introduction of frame_length field in XDP ctx to another series
- minor changes

Changes since v4:
- rebase ontop of bpf-next
- introduce xdp_shared_info to build xdp multi-buff instead of using the skb_shared_info struct
- introduce frame_length in xdp ctx
- drop previous bpf helpers
- fix bpf_xdp_adjust_tail for xdp multi-buff
- introduce xdp multi-buff self-tests for bpf_xdp_adjust_tail
- fix xdp_return_frame_bulk for xdp multi-buff

Changes since v3:
- rebase ontop of bpf-next
- add patch 10/13 to copy back paged data from a xdp multi-buff frame to userspace buffer for xdp multi-buff selftests

Changes since v2:
- add throughput measurements
- drop bpf_xdp_adjust_mb_header bpf helper
- introduce selftest for xdp multibuffer
- addressed comments on bpf_xdp_get_frags_count
- introduce xdp multi-buff support to cpumaps

Changes since v1:
- Fix use-after-free in xdp_return_{buff/frame}
- Introduce bpf helpers
- Introduce xdp_mb sample program
- access skb_shared_info->nr_frags only on the last fragment

Changes since RFC:
- squash multi-buffer bit initialization in a single patch
- add mvneta non-linear XDP buff support for tx side

[0] https://netdevconf.info/0x14/session.html?talk-the-path-to-tcp-4k-mtu-and-rx-zerocopy
[1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
[2] https://netdevconf.info/0x14/session.html?tutorial-add-XDP-support-to-a-NIC-driver (XDPmulti-buffers section)

Eelco Chaudron (3):
bpf: add multi-buff support to the bpf_xdp_adjust_tail() API
bpf: add multi-buffer support to xdp copy helpers
bpf: update xdp_adjust_tail selftest to include multi-buffer

Lorenzo Bianconi (15):
net: skbuff: add size metadata to skb_shared_info for xdp
xdp: introduce flags field in xdp_buff/xdp_frame
net: mvneta: update mb bit before passing the xdp buffer to eBPF layer
net: mvneta: simplify mvneta_swbm_add_rx_fragment management
net: xdp: add xdp_update_skb_shared_info utility routine
net: marvell: rely on xdp_update_skb_shared_info utility routine
xdp: add multi-buff support to xdp_return_{buff/frame}
net: mvneta: add multi buffer support to XDP_TX
net: mvneta: enable jumbo frames for XDP
bpf: introduce bpf_xdp_get_buff_len helper
bpf: move user_size out of bpf_test_init
bpf: introduce multibuff support to bpf_prog_test_run_xdp()
bpf: test_run: add xdp_shared_info pointer in bpf_test_finish
signature
net: xdp: introduce bpf_xdp_adjust_data helper
bpf: add bpf_xdp_adjust_data selftest

 drivers/net/ethernet/marvell/mvneta.c         | 204 ++++++++++-------
 include/linux/skbuff.h                        |   6 +-
 include/net/xdp.h                             |  95 +++++++-
 include/uapi/linux/bpf.h                      |  39 ++++
 kernel/trace/bpf_trace.c                      |   3 +
 net/bpf/test_run.c                            | 117 ++++++++--
 net/core/filter.c                             | 213 +++++++++++++++++-
 net/core/xdp.c                                |  76 ++++++-
 tools/include/uapi/linux/bpf.h                |  39 ++++
 .../bpf/prog_tests/xdp_adjust_data.c          |  55 +++++
 .../bpf/prog_tests/xdp_adjust_tail.c          | 118 ++++++++++
 .../selftests/bpf/prog_tests/xdp_bpf2bpf.c    | 151 +++++++++----
 .../bpf/progs/test_xdp_adjust_tail_grow.c     |  10 +-
 .../bpf/progs/test_xdp_adjust_tail_shrink.c   |  32 ++-
 .../selftests/bpf/progs/test_xdp_bpf2bpf.c    |   2 +-
 .../bpf/progs/test_xdp_update_frags.c         |  41 ++++
 16 files changed, 1036 insertions(+), 165 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_adjust_data.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_update_frags.c

Signature · 1 line

2.31.1