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

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Message-ID: <20090325175908.GA25518@elte.hu>
Date:	Wed, 25 Mar 2009 18:59:08 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Woodhouse <dwmw2@...radead.org>
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


* David Woodhouse <dwmw2@...radead.org> wrote:

> On Tue, 2009-03-24 at 21:32 +0100, Ingo Molnar wrote:
> > (Cc:s added)
> > 
> > * Andrew Lutomirski <amluto@...il.com> wrote:
> > 
> > > On vanilla 2.6.29 (on Ubuntu 8.10), on a Lenovo x200s, my system 
> > > is completely hosed on resume.  It appears that even hard disk IO 
> > > didn't work (trying to do *anything* including getting a dmesg 
> > > trace just spewed sda io errors to the console).  Hence no trace.  
> > > I did an alt-sysrq-b and the screen went blank and the machine 
> > > just started beeping at me.
> > > 
> > > Resume works much better with intel_iommu=off.  (I remember seeing 
> > > a patch go by that purported to fix resume with IOMMU enabled, but 
> > > it didn't work for me.)
> > > 
> > > I'd be happy to try to make a better bug report if anyone has any 
> > > bright ideas.
> > 
> > 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 ;-).

	Ingo
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