[vfio-users] Cannot fix Error 43 for GTX 680 passed through to win 10 guest

[Alex Williamson]

On Tue, 2015-10-13 at 18:06 +0000, root at yoshi.dynu.com wrote:
> qemu just crashes randomly at start without any error.
> 
> I am terribly sorry that i didn't had a look at my kernel messages after 
> launching a vm.
> 
> As soon as the nvidia driver tries to start a get numerous errors from 
> DMAR/DRHR trying to write at addresses.
> 
> here is a bin with all settings and dmesg output.
> 
> http://pastebin.com/0EJ5GKfD

Yes, the DMAR errors are surely a clue.  There's no chance you're
booting a 32-bit host kernel is there?  The DMA faults are all above 4G,
so one thing to try might be a smaller guest size, say 2G.  Another test
would be to prevent vfio from using larger IOMMU mappings via the
disable_hugepages=1 module option to vfio_iommu_type1.  BTW,
intel_iommu=verbose is not a valid option for the driver.  Thanks,

Alex