[Nouveau] Rewriting Intel PCI bridge prefetch base address bits solves nvidia graphics issues

[Daniel Drake]

On Tue, Aug 28, 2018 at 5:57 PM, Peter Wu <peter at lekensteyn.nl> wrote:
> Only non-bridge devices can be passed to a guest, but perhaps logging
> access to the emulated bridge is already sufficient. The Prefetchable
> Base Upper 32 Bits register is at offset 0x28.
>
> In a trace where the Nvidia device is disabled/enabled via Device
> Manager, I see writes on the enable path:
>
>     2571 at 1535108904.593107:rp_write_config (ioh3420, @0x28, 0x0, len=0x4)

Did you do anything special to get an emulated bridge included in this setup?

Folllowing the instructions at
https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF I can
successfully pass through devices to windows running under
virt-manager. In the nvidia GPU case I haven't got passed the driver
installation failure, but I can pass through other devices OK and
install their drivers.

However I do not end up with any PCI-to-PCI bridges in this setup. The
passed through device sits at address 00:08.0, parent is the PCI host
bridge 00:00.0.

(I'm trying to spy if Windows appears to restore or reset the PCI
bridge prefetch registers upon resume)

Thanks
Daniel