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Re: [Xen-users] Have you ever met this behavior with IGD passthrough?

On Fri, Jul 26, 2013 at 6:41 PM, Andrew Bobulsky <rulerof@xxxxxxxxx> wrote:
> On Fri, Jul 26, 2013 at 3:04 AM, G.R. <firemeteor@xxxxxxxxxxxxxxxxxxxxx> 
> wrote:
>> Hi guys,
>> I know that both of you are playing with IGD passthrough. So I would
>> like to check with you if I'm the only one that saw this behavior.
>> In my system, the panel becomes flickering rapidly with different
>> colors after domU starts. This lasts until the guest loads gfx driver.
>> There is a workaround by loading the VGA module in GRUB2, which
>> greatly shorten the time it flickers. But with a natively installed
>> windows guest, the flickering lasts until the OS get the login screen
>> prepared. But if the windows is not properly shutdown and the system
>> enters the repairing screen in next boot, you can simply see nothing
>> in this case.
>> This is not show-stopper but is quite annoying. But to my surprise, it
>> seems that nobody mentions this behavior in blogs / mail-lists. What's
>> your case then?
>> PS: Previously (e.g. xen 4.2.x), this flickering only happens happen
>> on a second guest boot and later-on (Per host reboot). I just upgraded
>> to xen 4.3.0, and haven't got chance to see if this behavior has
>> changed.
>> Thanks,
>> Timothy
> Hello Timothy,
> This is actually one of the more infuriating problems with secondary
> passthrough...  Windows Startup Repair will just sit there forever.
> To disable it, run the following command in your Windows DomU from an
> elevated command prompt:
>> bcdedit /set {default} recoveryenabled No

Thanks for the sharing. This absolutely helps.

> That will at least prevent your guest boot from getting hijacked.
> You said something about being able to fix that flickering problem by
> loading a GRUB2 module.   Does this module allow you to see bootloader
> output on a non-primary passedthrough GPU if you chainload the Windows
> Boot Manager from it?  That would be a pretty neat workaround!

I believe it's a different case for a secondary GPU passthrough.
If I understand correctly, you should still be able to see the boot
sequence in the VNC since the boot happens on the emulated primary VGA
which is still available in your case.

In my case, since the emulated VGA is totally replaced by the
passthrough device, I have no alternative if it does not work. (Linux
serial console is not discussed here)

I guess the VBIOS is not properly executed in my case, so the device
is not properly initialized until the guest driver is load.
Grub2 VGA module helps by performing some preliminary initialization.
But I believe it won't help in your case.


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