Re: [Xen-devel] question about i915 driver in dom0

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Friday, January 06, 2012 10:37 PM
> 
> > > > I hadn't seen it... but then my main desktop box where I run intensive
> > > > tests (ie, games) is radeon and nvidia so hadn't really tried seen this.
> > > > The box that has i915 just does some simple framebuffer manipulation
> and
> > > > that looks OK.
> > >
> > > yes, framebuffer console works well in my side too.
> 
> Good.
> > > > Do you see the same symptoms - checkboard screen?
> > >
> > > Not exactly. The screen becomes white, and then the system becomes
> > > unstable and hang several minutes later. It's possible that mine is a
> > > different issue than listed on the wiki page, since many reasons may
> > > finally reach the same symptom - GPU hang... :/
> >
> > well, there happens once with a checkboard screen, with the rest all
> > white screens.
> >
> > >
> > > >
> > > > The LKML had some fixes for this from Keith Packard. Something about
> > > > using i915.semaphores=0 I think. And I thought I saw some fixes for
> > > > 3.2-rc7 for this but not sure..
> > >
> > > I'll have a try on latest Linux on this. But I suspect that this may be a
> > > virtualization specific bug (e.g. similar gfn/mfn issue as nvidia case),
> > > because same dom0 image could run glxgear smoothly on bare metal.
> > >
> >
> > I used latest 3.2 release, no difference.
> 
> What is the motherboard you have? I just bought an "DQ67SW" which perhaps
> has the same video card?

I'm using a HP elitebook 8460p (Intel @ QM67 express chipset), with a HD 
graphics 3000.

> 
> 
> But more interestingly - are you building your kernel from scratch? There

yes

> was some requirements in having CONFIG_IOMMU_DMAR in the kernels -
> otherwise
> the intel-gtt.c would use the 'virt_to_phys' code instead of the DMA API.

Suppose you mean CONFIG_DMAR_TABLE? There's no CONFIG_IOMMU_DMAR
in the latest kernel. Yes, I didn't enable that option, and will have a try.

But a side question is, will enabling VT-d in dom0 conflict with Xen's own
VT-d operations?

> 
> And that caused an endless amount of pain.
> >
> > i915.semaphores=0 has no effect.
> >
> > But I observed below warnings in the boot process:
> > [    8.872430] [drm] MTRR allocation failed.  Graphics performance may
> suffer.
> > [   18.384552] microcode: CPU0 update to revision 0x1b failed
> >
> > Not sure whether above two issues may have impact on the said problem.
> > I know microcode update is still missing in upstream, but not sure about any
> 
> Right, microcode is ... pending hpa's coming back from paternity leave.
> > MTRR specific pending patches.
> 
> The MTRR are not in, but the graphics code should still work.

That's my feeling too...

Thanks
Kevin

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