Commit 84214ab4 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Daniel Borkmann
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igc: Enable and fix RX hash usage by netstack 

When function igc_rx_hash() was introduced in v4.20 via commit 0507ef8a
("igc: Add transmit and receive fastpath and interrupt handlers"), the
hardware wasn't configured to provide RSS hash, thus it made sense to not
enable net_device NETIF_F_RXHASH feature bit.

The NIC hardware was configured to enable RSS hash info in v5.2 via commit
2121c271 ("igc: Add multiple receive queues control supporting"), but
forgot to set the NETIF_F_RXHASH feature bit.

The original implementation of igc_rx_hash() didn't extract the associated
pkt_hash_type, but statically set PKT_HASH_TYPE_L3. The largest portions of
this patch are about extracting the RSS Type from the hardware and mapping
this to enum pkt_hash_types. This was based on Foxville i225 software user
manual rev-1.3.1 and tested on Intel Ethernet Controller I225-LM (rev 03).

For UDP it's worth noting that RSS (type) hashing have been disabled both for
IPv4 and IPv6 (see IGC_MRQC_RSS_FIELD_IPV4_UDP + IGC_MRQC_RSS_FIELD_IPV6_UDP)
because hardware RSS doesn't handle fragmented pkts well when enabled (can
cause out-of-order). This results in PKT_HASH_TYPE_L3 for UDP packets, and
hash value doesn't include UDP port numbers. Not being PKT_HASH_TYPE_L4, have
the effect that netstack will do a software based hash calc calling into
flow_dissect, but only when code calls skb_get_hash(), which doesn't
necessary happen for local delivery.

For QA verification testing I wrote a small bpftrace prog:
 [0] https://github.com/xdp-project/xdp-project/blob/master/areas/hints/monitor_skb_hash_on_dev.bt



Fixes: 2121c271 ("igc: Add multiple receive queues control supporting")
Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarSong Yoong Siang <yoong.siang.song@intel.com>
Link: https://lore.kernel.org/bpf/168182464270.616355.11391652654430626584.stgit@firesoul
parent 74fc8801

drivers/net/ethernet/intel/igc/igc.h

+28 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/ptp_clock_kernel.h>

#include <linux/timecounter.h>

#include <linux/net_tstamp.h>

#include <linux/bitfield.h>



#include "igc_hw.h"
@@ -311,6 +312,33 @@ extern char igc_driver_name[]; 
#define IGC_MRQC_RSS_FIELD_IPV4_UDP	0x00400000

#define IGC_MRQC_RSS_FIELD_IPV6_UDP	0x00800000



/* RX-desc Write-Back format RSS Type's */

enum igc_rss_type_num {

	IGC_RSS_TYPE_NO_HASH		= 0,

	IGC_RSS_TYPE_HASH_TCP_IPV4	= 1,

	IGC_RSS_TYPE_HASH_IPV4		= 2,

	IGC_RSS_TYPE_HASH_TCP_IPV6	= 3,

	IGC_RSS_TYPE_HASH_IPV6_EX	= 4,

	IGC_RSS_TYPE_HASH_IPV6		= 5,

	IGC_RSS_TYPE_HASH_TCP_IPV6_EX	= 6,

	IGC_RSS_TYPE_HASH_UDP_IPV4	= 7,

	IGC_RSS_TYPE_HASH_UDP_IPV6	= 8,

	IGC_RSS_TYPE_HASH_UDP_IPV6_EX	= 9,

	IGC_RSS_TYPE_MAX		= 10,

};

#define IGC_RSS_TYPE_MAX_TABLE		16

#define IGC_RSS_TYPE_MASK		GENMASK(3,0) /* 4-bits (3:0) = mask 0x0F */



/* igc_rss_type - Rx descriptor RSS type field */

static inline u32 igc_rss_type(const union igc_adv_rx_desc *rx_desc)

{

	/* RSS Type 4-bits (3:0) number: 0-9 (above 9 is reserved)

	 * Accessing the same bits via u16 (wb.lower.lo_dword.hs_rss.pkt_info)

	 * is slightly slower than via u32 (wb.lower.lo_dword.data)

	 */

	return le32_get_bits(rx_desc->wb.lower.lo_dword.data, IGC_RSS_TYPE_MASK);

}



/* Interrupt defines */

#define IGC_START_ITR			648 /* ~6000 ints/sec */

#define IGC_4K_ITR			980

drivers/net/ethernet/intel/igc/igc_main.c

+27 −4
Original line number Diff line number Diff line
@@ -1687,14 +1687,36 @@ static void igc_rx_checksum(struct igc_ring *ring, 
		   le32_to_cpu(rx_desc->wb.upper.status_error));

}



/* Mapping HW RSS Type to enum pkt_hash_types */

static const enum pkt_hash_types igc_rss_type_table[IGC_RSS_TYPE_MAX_TABLE] = {

	[IGC_RSS_TYPE_NO_HASH]		= PKT_HASH_TYPE_L2,

	[IGC_RSS_TYPE_HASH_TCP_IPV4]	= PKT_HASH_TYPE_L4,

	[IGC_RSS_TYPE_HASH_IPV4]	= PKT_HASH_TYPE_L3,

	[IGC_RSS_TYPE_HASH_TCP_IPV6]	= PKT_HASH_TYPE_L4,

	[IGC_RSS_TYPE_HASH_IPV6_EX]	= PKT_HASH_TYPE_L3,

	[IGC_RSS_TYPE_HASH_IPV6]	= PKT_HASH_TYPE_L3,

	[IGC_RSS_TYPE_HASH_TCP_IPV6_EX] = PKT_HASH_TYPE_L4,

	[IGC_RSS_TYPE_HASH_UDP_IPV4]	= PKT_HASH_TYPE_L4,

	[IGC_RSS_TYPE_HASH_UDP_IPV6]	= PKT_HASH_TYPE_L4,

	[IGC_RSS_TYPE_HASH_UDP_IPV6_EX] = PKT_HASH_TYPE_L4,

	[10] = PKT_HASH_TYPE_NONE, /* RSS Type above 9 "Reserved" by HW  */

	[11] = PKT_HASH_TYPE_NONE, /* keep array sized for SW bit-mask   */

	[12] = PKT_HASH_TYPE_NONE, /* to handle future HW revisons       */

	[13] = PKT_HASH_TYPE_NONE,

	[14] = PKT_HASH_TYPE_NONE,

	[15] = PKT_HASH_TYPE_NONE,

};



static inline void igc_rx_hash(struct igc_ring *ring,

			       union igc_adv_rx_desc *rx_desc,

			       struct sk_buff *skb)

{

	if (ring->netdev->features & NETIF_F_RXHASH)

		skb_set_hash(skb,

			     le32_to_cpu(rx_desc->wb.lower.hi_dword.rss),

			     PKT_HASH_TYPE_L3);

	if (ring->netdev->features & NETIF_F_RXHASH) {

		u32 rss_hash = le32_to_cpu(rx_desc->wb.lower.hi_dword.rss);

		u32 rss_type = igc_rss_type(rx_desc);



		skb_set_hash(skb, rss_hash, igc_rss_type_table[rss_type]);

	}

}



static void igc_rx_vlan(struct igc_ring *rx_ring,
@@ -6551,6 +6573,7 @@ static int igc_probe(struct pci_dev *pdev, 
	netdev->features |= NETIF_F_TSO;

	netdev->features |= NETIF_F_TSO6;

	netdev->features |= NETIF_F_TSO_ECN;

	netdev->features |= NETIF_F_RXHASH;

	netdev->features |= NETIF_F_RXCSUM;

	netdev->features |= NETIF_F_HW_CSUM;

	netdev->features |= NETIF_F_SCTP_CRC;