Re: PCI/VGA passthrough on >Xen-4.2 - (XEN) AMD-Vi: IO_PAGE_FAULT:

[Hans Mueller <mcbeagle@gmx.de>]

On Friday, 9. November 2012 16:33:47 Ian Campbell wrote:
> On Fri, 2012-11-09 at 16:25 +0000, Hans Mueller wrote:
> > On Thursday, 8. November 2012 20:02:51 feral wrote:
> > > Upgraded from Xen-4.1 to 4.2/4.3/4.3-unstable.  Tested against all
> > > three.
> > > 
> > > VGA passthrough previously working with 4.1 is no longer working with
> > > >4.2.
> > > 
> > > Setup - Working:
> > > Mint13, kernel-3.2.0-32, Xen-4.1 (from Ubuntu-Precise repos),
> > > libvirt-bin,
> > > xend
> > > Asus Radeon HD 7870 DirectCU.
> > > Works perfect.  Benches on par with bare metal.
> > > 
> > > Setup - Broken:
> > > Mint13, kernel-3.2.0-32, Xen-4.2,Xen-4.3,Xen-4.3-unstable (from GIT), xl
> > > toolstack.
> > > Asus Radeon HD 7870 DirectCU.
> > > Some times the guest boots correctly but display is never enabled.
> > > 
> > >  Sometimes BSOD, doesn't seem to be any rhyme or reason?
> > > 
> > > No errors in logs.   Found the following in 'xl dmesg':
> > > (XEN) AMD-Vi: IO_PAGE_FAULT: domain = 2, device id = 0x600, fault
> > > address =
> > > 0x1ac800000, flags = 0
> > 
> > I had a similar problem since hg revision 25818:50adc933faaf which changes
> > the qemu tag.
> > It looks like the qemu commit
> > 3e66da7266c84638c0e22a09c9d2b07529802576
> > (qemu-xen-trad: fix msi_translate with PV event delivery)
> > causes this behavior.
> > 
> > I solved the problem for me by using 'pci_msitranslate=0' in the domU
> > config.
>
> I don't follow this stuff closely but I could have sworn we had disabled
> msitranslate by default.

You're right - you don't have to explicitly disable msitranslate, you just may 
not enable it (which was the case in my domU config, not sure why it was 
enabled nor whether it was really required in the past - I think it was 
enabled during pci/gpu-passthrough testing and not changed back/disabled once 
it worked).