Re: Issue with Ath9k/PCI passthrough

[Christian Lamparter <chunkeey@gmail.com>]

On Monday, January 7, 2019 6:55:48 PM CET James Prestwood wrote:
> 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
> 

You could be a victim of:

|/*
| * Some Atheros AR9xxx and QCA988x chips do not behave after a bus reset.
| * The device will throw a Link Down error on AER-capable systems and
| * regardless of AER, config space of the device is never accessible again
| * and typically causes the system to hang or reset when access is attempted.
| * http://www.spinics.net/lists/linux-pci/msg34797.html
| */
|DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0030, quirk_no_bus_reset);
|DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0032, quirk_no_bus_reset);
|DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x003c, quirk_no_bus_reset);
|DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0033, quirk_no_bus_reset);
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/quirks.c#n3400>

I know that the AR93xx and AR94xx cards have problems with PCIe Passthrough:
<https://patchwork.kernel.org/patch/9141239/> and
<https://www.spinics.net/lists/linux-pci/msg34797.html> so maybe you can get
it to work, once you add a entry to the fixup list.

Regards,
Christian