[vfio-users] BIOS memory mapping or chipset issue with MMIO prevents IGD pass-through in legacy mode?

[globalgorrilla at fastmail.fm]

On Wed, Jul 27, 2016, at 06:04 PM, Alex Williamson wrote:

> Hmm, the kernel not exposing the VGA regions is really the only way we
> can fail here and the only two ways that the kernel won't expose VGA,
> given that enabled in the config, is if the device isn't VGA (which we
> can see by your class code, it is) or if the disable_vga option to
> vfio_pci is used.  You don't happen to have that left over from
> assigning discrete devices, do you?
> 
> # cat /sys/module/vfio_pci/parameters/disable_vga

Indeed I did, thanks! Now with it gone I still get the DMAR messages ...

[ 4683.644755] DMAR: DRHD: handling fault status reg 3
[ 4683.703123] DMAR: [DMA Read] Request device [00:02.0] fault addr
8f440000 [fault reason 06] PTE Read access is not set
[ 4683.831145] DMAR: DRHD: handling fault status reg 2
[ 4683.889487] DMAR: [DMA Read] Request device [00:02.0] fault addr
8f494000 [fault reason 06] PTE Read access is not set

... but I also get pass-through:

[ 4870.366423] kvm: zapping shadow pages for mmio generation wraparound
[ 4887.800200] vgaarb: device changed decodes:
PCI:0000:04:00.0,olddecodes=io+mem,decodes=io+mem:owns=none
[ 4887.800202] vgaarb: device changed decodes:
PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem

No output yet.   Is vgaarb looking correct above? 0000:04:00.0 is an R9
290.