6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit 02614eee26fbdfd73b944769001cefeff6ed008c ]
idpf has a limit on number of scatter-gather frags that can be used per segment.
Currently, idpf_tx_start() checks if the limit is hit and forces a linearization of the whole packet.
This requires high order allocations that can fail under memory pressure. A full size BIG-TCP packet would require order-7 alocation on x86_64 :/
We can move the check earlier from idpf_features_check() for TSO packets, to force GSO in this case, removing the cost of a big copy.
This means that a linearization will eventually happen with sizes smaller than one MSS.
__idpf_chk_linearize() is renamed to idpf_chk_tso_segment() and moved to idpf_lib.c
Signed-off-by: Eric Dumazet edumazet@google.com Cc: Przemek Kitszel przemyslaw.kitszel@intel.com Cc: Jacob Keller jacob.e.keller@intel.com Cc: Madhu Chittim madhu.chittim@intel.com Cc: Pavan Kumar Linga pavan.kumar.linga@intel.com Cc: Willem de Bruijn willemb@google.com Cc: Andrew Lunn andrew+netdev@lunn.ch Reviewed-by: Joshua Hay joshua.a.hay@intel.com Tested-by: Brian Vazquez brianvv@google.com Acked-by: Tony Nguyen anthony.l.nguyen@intel.com Link: https://patch.msgid.link/20250818195934.757936-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/idpf/idpf.h | 2 + drivers/net/ethernet/intel/idpf/idpf_lib.c | 102 +++++++++++++++- drivers/net/ethernet/intel/idpf/idpf_txrx.c | 129 ++++---------------- 3 files changed, 120 insertions(+), 113 deletions(-)
diff --git a/drivers/net/ethernet/intel/idpf/idpf.h b/drivers/net/ethernet/intel/idpf/idpf.h index a2b346d91879e..f4d51c885f335 100644 --- a/drivers/net/ethernet/intel/idpf/idpf.h +++ b/drivers/net/ethernet/intel/idpf/idpf.h @@ -144,6 +144,7 @@ enum idpf_vport_state { * @link_speed_mbps: Link speed in mbps * @vport_idx: Relative vport index * @max_tx_hdr_size: Max header length hardware can support + * @tx_max_bufs: Max buffers that can be transmitted with scatter-gather * @state: See enum idpf_vport_state * @netstats: Packet and byte stats * @stats_lock: Lock to protect stats update @@ -155,6 +156,7 @@ struct idpf_netdev_priv { u32 link_speed_mbps; u16 vport_idx; u16 max_tx_hdr_size; + u16 tx_max_bufs; enum idpf_vport_state state; struct rtnl_link_stats64 netstats; spinlock_t stats_lock; diff --git a/drivers/net/ethernet/intel/idpf/idpf_lib.c b/drivers/net/ethernet/intel/idpf/idpf_lib.c index 52d9caab2fcb2..371fc5052420d 100644 --- a/drivers/net/ethernet/intel/idpf/idpf_lib.c +++ b/drivers/net/ethernet/intel/idpf/idpf_lib.c @@ -742,6 +742,7 @@ static int idpf_cfg_netdev(struct idpf_vport *vport) np->vport_idx = vport->idx; np->vport_id = vport->vport_id; np->max_tx_hdr_size = idpf_get_max_tx_hdr_size(adapter); + np->tx_max_bufs = idpf_get_max_tx_bufs(adapter);
spin_lock_init(&np->stats_lock);
@@ -2205,6 +2206,92 @@ static int idpf_change_mtu(struct net_device *netdev, int new_mtu) return err; }
+/** + * idpf_chk_tso_segment - Check skb is not using too many buffers + * @skb: send buffer + * @max_bufs: maximum number of buffers + * + * For TSO we need to count the TSO header and segment payload separately. As + * such we need to check cases where we have max_bufs-1 fragments or more as we + * can potentially require max_bufs+1 DMA transactions, 1 for the TSO header, 1 + * for the segment payload in the first descriptor, and another max_buf-1 for + * the fragments. + * + * Returns true if the packet needs to be software segmented by core stack. + */ +static bool idpf_chk_tso_segment(const struct sk_buff *skb, + unsigned int max_bufs) +{ + const struct skb_shared_info *shinfo = skb_shinfo(skb); + const skb_frag_t *frag, *stale; + int nr_frags, sum; + + /* no need to check if number of frags is less than max_bufs - 1 */ + nr_frags = shinfo->nr_frags; + if (nr_frags < (max_bufs - 1)) + return false; + + /* We need to walk through the list and validate that each group + * of max_bufs-2 fragments totals at least gso_size. + */ + nr_frags -= max_bufs - 2; + frag = &shinfo->frags[0]; + + /* Initialize size to the negative value of gso_size minus 1. We use + * this as the worst case scenario in which the frag ahead of us only + * provides one byte which is why we are limited to max_bufs-2 + * descriptors for a single transmit as the header and previous + * fragment are already consuming 2 descriptors. + */ + sum = 1 - shinfo->gso_size; + + /* Add size of frags 0 through 4 to create our initial sum */ + sum += skb_frag_size(frag++); + sum += skb_frag_size(frag++); + sum += skb_frag_size(frag++); + sum += skb_frag_size(frag++); + sum += skb_frag_size(frag++); + + /* Walk through fragments adding latest fragment, testing it, and + * then removing stale fragments from the sum. + */ + for (stale = &shinfo->frags[0];; stale++) { + int stale_size = skb_frag_size(stale); + + sum += skb_frag_size(frag++); + + /* The stale fragment may present us with a smaller + * descriptor than the actual fragment size. To account + * for that we need to remove all the data on the front and + * figure out what the remainder would be in the last + * descriptor associated with the fragment. + */ + if (stale_size > IDPF_TX_MAX_DESC_DATA) { + int align_pad = -(skb_frag_off(stale)) & + (IDPF_TX_MAX_READ_REQ_SIZE - 1); + + sum -= align_pad; + stale_size -= align_pad; + + do { + sum -= IDPF_TX_MAX_DESC_DATA_ALIGNED; + stale_size -= IDPF_TX_MAX_DESC_DATA_ALIGNED; + } while (stale_size > IDPF_TX_MAX_DESC_DATA); + } + + /* if sum is negative we failed to make sufficient progress */ + if (sum < 0) + return true; + + if (!nr_frags--) + break; + + sum -= stale_size; + } + + return false; +} + /** * idpf_features_check - Validate packet conforms to limits * @skb: skb buffer @@ -2226,12 +2313,15 @@ static netdev_features_t idpf_features_check(struct sk_buff *skb, if (skb->ip_summed != CHECKSUM_PARTIAL) return features;
- /* We cannot support GSO if the MSS is going to be less than - * 88 bytes. If it is then we need to drop support for GSO. - */ - if (skb_is_gso(skb) && - (skb_shinfo(skb)->gso_size < IDPF_TX_TSO_MIN_MSS)) - features &= ~NETIF_F_GSO_MASK; + if (skb_is_gso(skb)) { + /* We cannot support GSO if the MSS is going to be less than + * 88 bytes. If it is then we need to drop support for GSO. + */ + if (skb_shinfo(skb)->gso_size < IDPF_TX_TSO_MIN_MSS) + features &= ~NETIF_F_GSO_MASK; + else if (idpf_chk_tso_segment(skb, np->tx_max_bufs)) + features &= ~NETIF_F_GSO_MASK; + }
/* Ensure MACLEN is <= 126 bytes (63 words) and not an odd size */ len = skb_network_offset(skb); diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c index 087a3077d5481..11bb61c123754 100644 --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c @@ -15,8 +15,28 @@ struct idpf_tx_stash { #define idpf_tx_buf_compl_tag(buf) (*(u32 *)&(buf)->priv) LIBETH_SQE_CHECK_PRIV(u32);
-static bool idpf_chk_linearize(struct sk_buff *skb, unsigned int max_bufs, - unsigned int count); +/** + * idpf_chk_linearize - Check if skb exceeds max descriptors per packet + * @skb: send buffer + * @max_bufs: maximum scatter gather buffers for single packet + * @count: number of buffers this packet needs + * + * Make sure we don't exceed maximum scatter gather buffers for a single + * packet. + * TSO case has been handled earlier from idpf_features_check(). + */ +static bool idpf_chk_linearize(const struct sk_buff *skb, + unsigned int max_bufs, + unsigned int count) +{ + if (likely(count <= max_bufs)) + return false; + + if (skb_is_gso(skb)) + return false; + + return true; +}
/** * idpf_buf_lifo_push - push a buffer pointer onto stack @@ -2575,111 +2595,6 @@ int idpf_tso(struct sk_buff *skb, struct idpf_tx_offload_params *off) return 1; }
-/** - * __idpf_chk_linearize - Check skb is not using too many buffers - * @skb: send buffer - * @max_bufs: maximum number of buffers - * - * For TSO we need to count the TSO header and segment payload separately. As - * such we need to check cases where we have max_bufs-1 fragments or more as we - * can potentially require max_bufs+1 DMA transactions, 1 for the TSO header, 1 - * for the segment payload in the first descriptor, and another max_buf-1 for - * the fragments. - */ -static bool __idpf_chk_linearize(struct sk_buff *skb, unsigned int max_bufs) -{ - const struct skb_shared_info *shinfo = skb_shinfo(skb); - const skb_frag_t *frag, *stale; - int nr_frags, sum; - - /* no need to check if number of frags is less than max_bufs - 1 */ - nr_frags = shinfo->nr_frags; - if (nr_frags < (max_bufs - 1)) - return false; - - /* We need to walk through the list and validate that each group - * of max_bufs-2 fragments totals at least gso_size. - */ - nr_frags -= max_bufs - 2; - frag = &shinfo->frags[0]; - - /* Initialize size to the negative value of gso_size minus 1. We use - * this as the worst case scenario in which the frag ahead of us only - * provides one byte which is why we are limited to max_bufs-2 - * descriptors for a single transmit as the header and previous - * fragment are already consuming 2 descriptors. - */ - sum = 1 - shinfo->gso_size; - - /* Add size of frags 0 through 4 to create our initial sum */ - sum += skb_frag_size(frag++); - sum += skb_frag_size(frag++); - sum += skb_frag_size(frag++); - sum += skb_frag_size(frag++); - sum += skb_frag_size(frag++); - - /* Walk through fragments adding latest fragment, testing it, and - * then removing stale fragments from the sum. - */ - for (stale = &shinfo->frags[0];; stale++) { - int stale_size = skb_frag_size(stale); - - sum += skb_frag_size(frag++); - - /* The stale fragment may present us with a smaller - * descriptor than the actual fragment size. To account - * for that we need to remove all the data on the front and - * figure out what the remainder would be in the last - * descriptor associated with the fragment. - */ - if (stale_size > IDPF_TX_MAX_DESC_DATA) { - int align_pad = -(skb_frag_off(stale)) & - (IDPF_TX_MAX_READ_REQ_SIZE - 1); - - sum -= align_pad; - stale_size -= align_pad; - - do { - sum -= IDPF_TX_MAX_DESC_DATA_ALIGNED; - stale_size -= IDPF_TX_MAX_DESC_DATA_ALIGNED; - } while (stale_size > IDPF_TX_MAX_DESC_DATA); - } - - /* if sum is negative we failed to make sufficient progress */ - if (sum < 0) - return true; - - if (!nr_frags--) - break; - - sum -= stale_size; - } - - return false; -} - -/** - * idpf_chk_linearize - Check if skb exceeds max descriptors per packet - * @skb: send buffer - * @max_bufs: maximum scatter gather buffers for single packet - * @count: number of buffers this packet needs - * - * Make sure we don't exceed maximum scatter gather buffers for a single - * packet. We have to do some special checking around the boundary (max_bufs-1) - * if TSO is on since we need count the TSO header and payload separately. - * E.g.: a packet with 7 fragments can require 9 DMA transactions; 1 for TSO - * header, 1 for segment payload, and then 7 for the fragments. - */ -static bool idpf_chk_linearize(struct sk_buff *skb, unsigned int max_bufs, - unsigned int count) -{ - if (likely(count < max_bufs)) - return false; - if (skb_is_gso(skb)) - return __idpf_chk_linearize(skb, max_bufs); - - return count > max_bufs; -}
/** * idpf_tx_splitq_get_ctx_desc - grab next desc and update buffer ring