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

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Message-Id: <1238004228.2085.56.camel@macbook.infradead.org>
Date:	Wed, 25 Mar 2009 18:03:48 +0000
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:
> 
> 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 ;-).

Yeah, trusting BIOS monkeys for this was always going to be a bad plan.
We should have just known how to set/read the damn hardware BARs -- the
most likely explanation for this is that your BIOS is just lying to you
about where it put the registers, I believe.

I'd like to put in a basic sanity check when we first ioremap the
(alleged) DMAR registers. Hopefully, the output I asked for will confirm
that there's a simple way to do that...

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

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