[vfio-users] How to set PCI address in "options vfio-pci" ?

[Kyle Marek]

On 05/17/2018 10:27 AM, Alex Williamson wrote:
> On Thu, 17 May 2018 12:56:49 +0800
> Eddie Yen <missile0407 at gmail.com> wrote:
>
>> Hi everyone,
>>
>> IME, you can set VID:PID by adding "options vfio-pci" into conf file and
>> put at modprobe.d
>> So that VFIO can take over the device that had same VID:PID when boot.
>>
>> But how can I set this option by using PCI Address without using override
>> script?
> There's no such module option, what's wrong with a script?  Part of the
> reason we don't have such a module option is that PCI addresses are not
> persistent, they can change based on devices added or removed, or even
> motherboard BIOS updates.  Userspace has more flexibility for managing
> this and is fully able to do so via initrd scripts and modprobe.d.
> Thanks,
>
> Alex

That's a good point.

However, I had an environment where I needed to pass through one of two
devices with the same PCI IDs. I accomplished it with an install command
in my modprobe config.

I can probably make this look at other factors before overriding the
driver, but the following config might work well enough if the PCI IDs
don't change:

# For each PCI device listed in the for-loop, override their assigned driver
# to vfio-pci, for usage with PCI-passthrough.
#
# Please make sure to include vfio-pci in the initrd, or some other modules
# will likely claim the devices first. This can be done on systems that use
# initramfs-tools by adding "vfio-pci" to /etc/initramfs-tools/modules
install vfio-pci for dev in 0000:03:00.0 0000:03:00.1; do echo vfio-pci > "/sys/bus/pci/devices/$dev/driver_override"; done; /sbin/modprobe --ignore-install vfio-pci $CMDLINE_OPTS

# Load vfio-pci before some other drivers so they don't claim devices first.
# The pre-drm line should handle all graphics drivers.
softdep snd_hda_intel pre: vfio-pci
softdep drm pre: vfio-pci


This worked well for me in dracut and initramfs-tools initrds with the
vfio-pci module included.