Re: [PATCH] irqchip/gic-v3-its: Enable dynamic MSI-X allocation

[Vlad Poenaru]

Hi,

Commit 0d6a7c417983 ("irqchip/gic-v3-its: Enable dynamic MSI-X
allocation"), merged for v7.3-rc1, breaks bnxt_en on our loving Grace
machines. Reverting it fixes the problem on current mainline.

Hardware:
  - NVIDIA Grace (Neoverse V2), ACPI, GICv3 + ITS
  - Broadcom BCM57508 (BCM957508-N1200FJ), FW 230.0.165.3, bnxt_en
  - The same platform with a Mellanox NIC (mlx5) is not affected

The trigger is a ring resize: a boot-time udev .link file with
RxBufferSize=max, i.e. "ethtool -G eth0 rx 4095 tx 4095". The close
path never gets the HWRM_RING_FREE completions, then TX times out and
the machine hangs:

  [   58.221] bnxt_en 0002:01:00.0 eth0: Resp cmpl intr err msg: 0x51
  [   58.221] bnxt_en 0002:01:00.0 eth0: hwrm_ring_free type 1 failed. rc:fffffff0 err:0
  ... (repeats every ~3.7s for every ring)
  [  215.539] bnxt_en 0002:01:00.0 eth0: NETDEV WATCHDOG: CPU: 69: transmit queue 18 timed out 5118 ms
  [  215.539] bnxt_en 0002:01:00.0 eth0: TX timeout detected, starting reset task!

Bisecting v7.2..v7.3-rc3 on this machine points at the irq-drivers
merge (8b5d31123f41), and within it:

  good: 9023960b74ab ("irqchip: Remove redundant dev_err()/dev_err_probe()")
  bad:  0d6a7c417983 ("irqchip/gic-v3-its: Enable dynamic MSI-X allocation")

On current mainline (f47d223627f8) the same machine fails at ~55s;
with the commit reverted it runs cleanly.

So far it only reproduces with our debug config (KASAN, lockdep,
DEBUG_PAGEALLOC, DMA_API_DEBUG, CPUMASK_OFFSTACK, ...), not with our
production config. I haven't narrowed down which option matters.

My guess is that with pci_msix_can_alloc_dyn() now true behind the ITS,
bnxt switches to dynamic MSI-X allocation and something on that path
loses the completion interrupts, but I haven't root-caused it.

Happy to test patches or collect more data.

Reported-by: Andrew Preece <apreece@xxxxxxxx>

#regzbot introduced: 0d6a7c417983b

Thanks,
Vlad