Affinity hints were being set to CPUs in local NUMA node first, and then
in other CPUs. This was creating 2 unintended issues:
1. Channels created to be assigned each to a different physical core
   were assigned to hyperthreading siblings because of being in same
   NUMA node.
   Since the patch previous to this one, this did not longer happen
   with default rss_cpus modparam because less channels are created.
2. XDP channels could be assigned to CPUs in different NUMA nodes,
   decreasing performance too much (to less than half in some of my
   tests).

This patch sets the affinity hints spreading the channels only in local
NUMA node's CPUs. A fallback for the case that no CPU in local NUMA node
is online has been added too.

Example of CPUs being assigned in a non optimal way before this and the
previous patch (note: in this system, xdp-8 to xdp-15 are created
because num_possible_cpus == 64, but num_present_cpus == 32 so they're
never used):

$ lscpu | grep -i numa
NUMA node(s):                    2
NUMA node0 CPU(s):               0-7,16-23
NUMA node1 CPU(s):               8-15,24-31

$ grep -H . /proc/irq/*/0000:07:00.0*/../smp_affinity_list
/proc/irq/141/0000:07:00.0-0/../smp_affinity_list:0
/proc/irq/142/0000:07:00.0-1/../smp_affinity_list:1
/proc/irq/143/0000:07:00.0-2/../smp_affinity_list:2
/proc/irq/144/0000:07:00.0-3/../smp_affinity_list:3
/proc/irq/145/0000:07:00.0-4/../smp_affinity_list:4
/proc/irq/146/0000:07:00.0-5/../smp_affinity_list:5
/proc/irq/147/0000:07:00.0-6/../smp_affinity_list:6
/proc/irq/148/0000:07:00.0-7/../smp_affinity_list:7
/proc/irq/149/0000:07:00.0-8/../smp_affinity_list:16
/proc/irq/150/0000:07:00.0-9/../smp_affinity_list:17
/proc/irq/151/0000:07:00.0-10/../smp_affinity_list:18
/proc/irq/152/0000:07:00.0-11/../smp_affinity_list:19
/proc/irq/153/0000:07:00.0-12/../smp_affinity_list:20
/proc/irq/154/0000:07:00.0-13/../smp_affinity_list:21
/proc/irq/155/0000:07:00.0-14/../smp_affinity_list:22
/proc/irq/156/0000:07:00.0-15/../smp_affinity_list:23
/proc/irq/157/0000:07:00.0-xdp-0/../smp_affinity_list:8
/proc/irq/158/0000:07:00.0-xdp-1/../smp_affinity_list:9
/proc/irq/159/0000:07:00.0-xdp-2/../smp_affinity_list:10
/proc/irq/160/0000:07:00.0-xdp-3/../smp_affinity_list:11
/proc/irq/161/0000:07:00.0-xdp-4/../smp_affinity_list:12
/proc/irq/162/0000:07:00.0-xdp-5/../smp_affinity_list:13
/proc/irq/163/0000:07:00.0-xdp-6/../smp_affinity_list:14
/proc/irq/164/0000:07:00.0-xdp-7/../smp_affinity_list:15
/proc/irq/165/0000:07:00.0-xdp-8/../smp_affinity_list:24
/proc/irq/166/0000:07:00.0-xdp-9/../smp_affinity_list:25
/proc/irq/167/0000:07:00.0-xdp-10/../smp_affinity_list:26
/proc/irq/168/0000:07:00.0-xdp-11/../smp_affinity_list:27
/proc/irq/169/0000:07:00.0-xdp-12/../smp_affinity_list:28
/proc/irq/170/0000:07:00.0-xdp-13/../smp_affinity_list:29
/proc/irq/171/0000:07:00.0-xdp-14/../smp_affinity_list:30
/proc/irq/172/0000:07:00.0-xdp-15/../smp_affinity_list:31

CPUs assignments after this and previous patch, so normal channels
created only one per core in NUMA node and affinities set only to local
NUMA node:

$ grep -H . /proc/irq/*/0000:07:00.0*/../smp_affinity_list
/proc/irq/116/0000:07:00.0-0/../smp_affinity_list:0
/proc/irq/117/0000:07:00.0-1/../smp_affinity_list:1
/proc/irq/118/0000:07:00.0-2/../smp_affinity_list:2
/proc/irq/119/0000:07:00.0-3/../smp_affinity_list:3
/proc/irq/120/0000:07:00.0-4/../smp_affinity_list:4
/proc/irq/121/0000:07:00.0-5/../smp_affinity_list:5
/proc/irq/122/0000:07:00.0-6/../smp_affinity_list:6
/proc/irq/123/0000:07:00.0-7/../smp_affinity_list:7
/proc/irq/124/0000:07:00.0-xdp-0/../smp_affinity_list:16
/proc/irq/125/0000:07:00.0-xdp-1/../smp_affinity_list:17
/proc/irq/126/0000:07:00.0-xdp-2/../smp_affinity_list:18
/proc/irq/127/0000:07:00.0-xdp-3/../smp_affinity_list:19
/proc/irq/128/0000:07:00.0-xdp-4/../smp_affinity_list:20
/proc/irq/129/0000:07:00.0-xdp-5/../smp_affinity_list:21
/proc/irq/130/0000:07:00.0-xdp-6/../smp_affinity_list:22
/proc/irq/131/0000:07:00.0-xdp-7/../smp_affinity_list:23
/proc/irq/132/0000:07:00.0-xdp-8/../smp_affinity_list:0
/proc/irq/133/0000:07:00.0-xdp-9/../smp_affinity_list:1
/proc/irq/134/0000:07:00.0-xdp-10/../smp_affinity_list:2
/proc/irq/135/0000:07:00.0-xdp-11/../smp_affinity_list:3
/proc/irq/136/0000:07:00.0-xdp-12/../smp_affinity_list:4
/proc/irq/137/0000:07:00.0-xdp-13/../smp_affinity_list:5
/proc/irq/138/0000:07:00.0-xdp-14/../smp_affinity_list:6
/proc/irq/139/0000:07:00.0-xdp-15/../smp_affinity_list:7

Signed-off-by: Íñigo Huguet <redacted>
---
 drivers/net/ethernet/sfc/efx_channels.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
index ec6c2f231e73..ef3168fbb5a6 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c

@@ -387,10 +387,18 @@ void efx_set_interrupt_affinity(struct efx_nic *efx)
 {
 	struct efx_channel *channel;
 	unsigned int cpu;
+	int numa_node = pcibus_to_node(efx->pci_dev->bus);
+	const struct cpumask *numa_mask = cpumask_of_node(numa_node);
 
+	/* If no online CPUs in local node, fallback to any online CPU */
+	if (cpumask_first_and(cpu_online_mask, numa_mask) >= nr_cpu_ids)
+		numa_mask = cpu_online_mask;
+
+	cpu = -1;
 	efx_for_each_channel(channel, efx) {
-		cpu = cpumask_local_spread(channel->channel,
-					   pcibus_to_node(efx->pci_dev->bus));
+		cpu = cpumask_next_and(cpu, cpu_online_mask, numa_mask);
+		if (cpu >= nr_cpu_ids)
+			cpu = cpumask_first_and(cpu_online_mask, numa_mask);
 		irq_set_affinity_hint(channel->irq, cpumask_of(cpu));
 	}
 }

-- 
2.31.1