Re: [Xen-devel] Q77 IGD instantly crashes on xen-pciback bind.

["Dr. Greg Wettstein" <greg@xxxxxxxxxxxxxxxxx>]

On Nov 24,  1:28pm, Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= wrote:

> Hello,

Hi, hope the week is going well for everyone.

> > >> As I was walking out the door I remembered I had been delinquent
> > >> with information.  The dom0 kernel is 32-bit 3.14.22 straight from
> > >> kernel.org under a 64-bit hypervisor compiled from 4.4.1 sources.
> > 
> > > Wow, quite an old thread :)
> > >  
> > > So you're still seeing the same problem with recent Xen/Linux
> > > versions.. 
> > 
> > Yes, the perils of platforming for 7 year field deployments... :-)
> > 
> > I can certainly build up a toolchain against the HEAD of XEN git and
> > the most recent release of the kernel if everyone feels that would be
> > beneficial.
> > 
> > > This might be a stupid question, but here goes anyway: Do you have
> > > serial console set up? And all the debug/verbose options specified
> > > for Xen and Linux?
> > 
> > The platform in question doesn't have any serial ports, at least not
> > surfaced.  We will need to do a bit of wiring if we need to go in that
> > direction.

> You mentioned it's Intel Q77 chipset based motherboard..  which
> means it should have Intel AMT functionality, which provides SOL
> (Serial-over-LAN), which you can use as a serial console for Xen.
>
> There are tools (at least amtterm) that you can use on another box
> to connect to the AMT SOL remotely..

So we wired up serial console connectivity to the test box and
repeated the VGA device binding with loglvl=all.  We lost the box
immediately without anything being written to the logs.

So we went hunting.

Interestingly the problem appears to be secondary to a BIOS
configuration option.  This may be specific to this platform but we
wanted to get it documented in the thread in case anyone else runs
into this.

The DQ77KB BIOS we are using has an option for 'IGD flat panel
display'.  The default option is LVDS, setting this to 'disabled'
clears the problem.

I haven't run down where things go wrong in pci_stub but I assume it
does something to the hardware which causes a problem when the video
controller is reset and then shutdown.

> > Now that I have the machine in a harness in the lab I will stick a
> > '#define DEBUG 1' in the top of drivers/xen/xen-pciback/pci_stub.c
> > since that is where the action seems to be going on.
> > 
> > The platform is headed for a measured computing environment so I
> > thought there may be some type of conflict with tboot holding a
> > reference to the VGA driver but I verified the issue in a straight
> > hypervisor boot.
> > 
> > I see that Tiejun Chen from Intel is sorting out issues with respect
> > to the need to export the ISA bridge into the device emulator in order
> > to support passthrough on these IGD devices.  I bound the 00:1f.0 ISA
> > bridge device to pciback and that worked but it did not change the
> > behavior of the regression.  When the 00:02.0 device is bound to
> > pciback the display is cleared and the machine dies in its tracks.

> Yeah, Tiejun is working on upstreaming the IGD passthru patches to
> Qemu-upstream.
>
> Qemu-dm-traditional already has (most of) the IGD passthru patches. 
> 
> Hope that helps,

So we are obviously working with qemu-dm-traditional and with the
IGD/LVDS BIOS configuration issue fixed the adapater passthrough is
working and Windows7 is coming up and detecting the IGD as a standard
VGA display adapter.  Additional invocations of the VM after the first
one result in failed passthrough with a garbled display.

I spent an afternoon wandering through the mailing lists and found
what I think are the two patches which are needed to map the 00:1f.0
ISA bridge device into the guest.  From the discussions surrounding
those patches it appears as if the Windows HD driver needs addresses
managed by that bridge to recognize the IGD device.

I will get those patches wired into qemu-dm-traditional and tested in
between whisky, wine, turkey and napping today.... :-)

I'm hoping that this positively impacts the ability to execute
multiple sessions.  I will report back the results so we have all of
this in the mailing list record.

> -- Pasi

Thanks for offering the pointers, have a good day.

Greg

}-- End of excerpt from Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?=

As always,
Dr. G.W. Wettstein, Ph.D.   Enjellic Systems Development, LLC.
4206 N. 19th Ave.           Specializing in information infra-structure
Fargo, ND  58102            development.
PH: 701-281-1686
FAX: 701-281-3949           EMAIL: greg@xxxxxxxxxxxx
------------------------------------------------------------------------------
"Immortality is an adequate definition of high availability for me."
                                -- Gregory F. Pfister


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