linux-kernel - Re: 2.6.29: can't resume from suspend with DMAR (intel iommu) enabled

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Message-Id: <1239051362.22733.87.camel@macbook.infradead.org>
Date:	Mon, 06 Apr 2009 13:56:01 -0700
From:	David Woodhouse <dwmw2@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andrew Lutomirski <amluto@...il.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Kyle McMartin <kyle@...hat.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Mark Gross <mgross@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.29: can't resume from suspend with DMAR (intel iommu)
 enabled

On Wed, 2009-03-25 at 18:59 +0100, Ingo Molnar wrote:
> > > i have a Lenovo T500 that does not even boot with with DMAR enabled 
> > > in the BIOS (it's default-off), i get this panic in early bootup:
> > > 
> > >     DMAR hardware is malfunctioning
> > 
> > Can you show me the output of the pr_debug() statement at 
> > dmar.c:543 (in alloc_iommu()?
> 
> that's not easy - i use it right now :)
> 
> That's another reason why warnings and non-panic() behavior are 
> better for developers too. Had it not crashed i could have sent you 
> my dmesg and i would not have turned off DMAR in the BIOS.
> 
> Now it's turned off in my BIOS (first barrier) and i need to reboot 
> the kernel (second barrier) and i need to hack up a kernel in a 
> certain way to produce debug info (third barrier) - in the merge 
> window (fourth barrier ;-).

If you manage to get a chance to do this after the merge window closes,
that would be much appreciated.

I have a T400 now, which will help with certain things (at least I have
a machine on which I can test suspend/resume). But I don't think I can
reproduce your panic on it.

Dirk reported the same panic, but we've just turned his iommu back on
and completely failed to reproduce the problem -- so I'm kind of stuck.

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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