eth: bnxt: preserve IRQ affinity across IRQ reallocation

Reconfiguring the rings frees the MSI-X vectors and allocates them
again. The IRQ descriptors go away with them, so the affinity user
space set is silently replaced by the driver's default NUMA spread.
This is painful to deal with for user space as seemingly arbitrary
NIC configuration changes lead to loss of configuration.

In NIPA (netdev CI) this results in the toeplitz test reporting:

  Exception| net.lib.py.ksft.KsftFailEx: IRQ170 is not mapped to a single core: 0-31

if the test run after another test which reconfigured the device.
We configure the IRQ mapping at boot, but if the driver is not
preserving the config - it gets lost.

Record the affinity in the notifier and apply it when the IRQs are
requested again. The notifier has to be registered unconditionally
now, so far it was only installed when TPH was enabled. Drivers
which let the core manage the affinity (idpf, ice, iavf via
netif_set_affinity_auto()) work exactly like this,
napi_restore_config() reapplies napi_config.affinity_mask on every
napi_enable().

Note that the affinity is supposed to follow the NAPI / queue,
same as the napi_config behavior in drivers mentioned above.
If the user changes the affinity when the device is down -
we will override it on up. That's expected, the IRQs are not
associated with queues when device is down (no name, no entry
in /proc/interrupts, no entry in netdev netlink).

map_idx is ulp_msix + i, so the slot shifts whenever RoCE takes
or releases vectors and the mask would end up on a different ring.
Key using the completion ring id, which maps to the NAPI instance.

Note2: this restores the side effect fcf42409c6e1 ("bnxt_en: use
irq_update_affinity_hint()") removed, but not the problem it was
fixing. The complaint there was that reopening the device resets
the affinity and can move an IRQ onto a CPU irqbalance was told
to stay away from. We now replay what user space or irqbalance
last asked for, the driver's own placement is only used for
a ring nobody has configured.

Note3: the combined irq_set_affinity_and_hint() looks like
it may hide the failure from __irq_set_affinity(), but let's
assume the IRQ maintainers know what their doing - either
this can't happen or is intentional.

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Link: https://patch.msgid.link/20260813193248.2578626-3-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions