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

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

On Nov 27, 12:11pm, Sander Eikelenboom wrote:
} Subject: Re: [Xen-devel] Q77 IGD instantly crashes on xen-pciback bind.

Hi, hope the week has gone well for everyone.

> > 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.

> This is probably due to the current lack of slot/bus reset in
> xen-pciback, Konrad has a preliminary kernel patch for xen-pciback
> that does this.  I have attached the patch, though it has some rough
> edges in the design :-)
>
> I'm currently running with his 3.19 xen-pciback patches series + the
> preliminary patch for slot/bus reset and rebooting a guest with
> vga/pci passthrough now works. (i'm running with a radeon card,
> passed through as a secondary card to the emulated qemu one, in a
> linux guest using qemu-xen, so i can't help you with your other
> questions and problems).

Thanks for taking the time for respond and forward along the patch.

I back ported the do_flr patch into the 3.14.x kernel and spent some
time working with it.  I thought it might be useful to others to
document what we ran into.

First of all the issue with the unsuccessful boot of Windows after the
first invocation doesn't appear to have anything to do with resetting
the card.  This was fixed by installing the most recent version of the
Intel HD drivers in the Windows guest.

If IGD passthrough is done without the HD drivers Windows 7 appears to
use its standard VGA driver which seems to be able to initialize and
run the IGD device but does not appear to shutdown the device in a
manner in which it can be re-started.  After the first invocation of
the guest is shutdown the screen goes to a solid color.  Subsequent
invocations result in the flashing multi-color screens which others
have documented.

With the HD drivers installed IGD passthrough works fine through
multiple invocations of a guest with the stock xen-pciback in 3.14.x.
We ran 40-50 repetitive Windows guest invocations and every one was
completely deterministic.

That being said we ran into an issue which we wanted to bounce off the
list in the context of this thread.

One of the things we were not able to do was to successfuly re-start
the IGD display for dom0.  After spending a lot of time going through
Konrad's reset code it appears the IGD devices in the Q77 and Q87
chipset implementations we are looking at are not advertising reset
functions which can be used.

It appears that the IGD devices are advertising that they need a
Device Specific Initialization (DSI) sequence in order to be enabled
or powered up, if we interpret the output of lscpi properly, ie:

---------------------------------------------------------------------------
00:02.0 VGA compatible controller: Intel Corporation Device 0152 (rev 09) 
(prog-if 00 [VGA controller])
        Subsystem: Intel Corporation Device 2036
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort-
<MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Interrupt: pin A routed to IRQ 11
        Region 0: Memory at f7800000 (64-bit, non-prefetchable) [size=4M]
        Region 2: Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Region 4: I/O ports at f000 [size=64]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: [90] MSI: Mask- 64bit- Count=1/1 Enable-
                Address: 00000000  Data: 0000
        Capabilities: [d0] Power Management version 2
                Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA 
PME(D0-,D1-,D2-,D3hot-,D3cold-)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME-
        Capabilities: [a4] PCIe advanced features <?>
---------------------------------------------------------------------------

The ATI adapters which we have a lot of passthrough experience with
are FLR capable and can be re-enabled after passthrough by writing a
'1' to the enable pseudo-file in the /sys/bus/pci/devices/BDF
directory.  The IGD adapters seem to fail to respond to a request to
be re-enabled.

We would certainly be interested in any suggestions the collective may
have with respect to how to get the adapter turned back on and/or
implement a reset.

> Sander

Have a good weekend.

Greg

}-- End of excerpt from Sander Eikelenboom

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
------------------------------------------------------------------------------
"Laugh now but you won't be laughing when we find you laying on the
 side of the road dead."
                                -- Betty Wettstein
                                   At the Lake

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