Message-ID: <6cc1ddae1bab8f71daa07c2c7082354507496f5f.camel@linux.intel.com>
Subject: Issue with Ath9k/PCI passthrough
From:   James Prestwood <james.prestwood@linux.intel.com>
To:     linux-wireless@vger.kernel.org
Date:   Mon, 07 Jan 2019 09:55:48 -0800
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Sender: linux-wireless-owner@vger.kernel.org
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Hi,

I am passing through PCI wireless adapters into a qemu VM and I am
seeing my host machine lock up/freeze when starting qemu if I try and
pass through an Atheros AR5B22 PCI card. After reboot I don't see
anything suspicious in /var/log/kern.log, although I don't really know
what to look for either (or maybe there is another log to look at?). I
have successfully done PCI passthrough with both an Intel 7260 and
3160. Its whenever I add the Atheros card into the mix (or by itself) I
get this lockup when starting the VM.

I have enabled the Ath9k drivers when building the kernel (same as with
Intel cards). This page I read online (https://wiki.debian.org/ath9k)
said the Ath9k cards don't require firmware like the Intel cards do, so
I have not added any firmware binaries for this card into the kernel
build. I also tried turning on the Ath9k debugging but saw no
additional prints in kern.log.

With PCI passthrough there is some configuration required, like
substituting the drivers for the vfio-pci driver on the host machine,
so it could be completely unrelated to the Ath9k driver. Still, I was
hoping that someone more knowledgeable than me may know whats going on,
or at least where to look. The fact that the Intel cards work fine was
what made me think it could be a driver problem.

I am more or less following this guide (except with wifi adapters
rather than GPU):
https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF

Using a custom built kernel based on 4.19.

Thanks,
James