Ath9k hang with pci passthrough

Ath9k hang with pci passthrough

[James Prestwood]

Hi,

This is a followup to my original PCI passthrough issue, which has been
resolved, though not as smoothly as I would like. Here is a brief
recap:

I am using PCI passthrough to a VM with an Ath9k wifi adapter. This was
causing my host machine to lock up/freeze when starting the VM. Adding
a line to drivers/pci/quirks.c resolve the issue. Here is the original
thread:

https://marc.info/?l=linux-wireless&m=154689580213002&w=2

By "resolved" I mean the host doesn't lock up, but I am still seeing
weird behavior. When starting the VM I see this:

qemu-system-x86_64: vfio-pci: Cannot read device rom at 0000:08:00.0
Device option ROM contents are probably invalid (check dmesg).
Skip option ROM probe with rombar=0, or load from file with romfile=
[    5.312843] irq 11: nobody cared (try booting with the "irqpoll"
option)
[    5.312843] handlers:
[    5.312843] [<0000000002e29ed0>] vp_interrupt
[    5.312843] [<00000000d9d80d45>] ath_isr
[    5.312843] Disabling IRQ #11

At this point it hangs for a minute or two, sometimes re-printing the
same "irq 11: nobody cared" message with a stack trace (sometimes up to
3 times). But eventually it boots into the VM and the adapter appears
to work as expected.

I have tried to get rid of the ROM contents print by adding "rombar=0",
which didn't seem to change anything. Similarly I tried "irqpoll" which
again didn't change the behavior (note both changes were on the guest
kernel boot, not host).

I don't see any such prints in my host kernel log during boot, so it
seems to be specific to PCI passthrough.

Since the adapter appears to work I could care less about these prints,
I am just hoping to resolve the 1-2min hang when booting the VM.

Thanks,
James