linux-kernel - Re: [regression, bisected] fails to boot on Dell Optiplex 760 with VT-d enabled

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Message-ID: <4A89E63E.407@debian.org>
Date:	Tue, 18 Aug 2009 02:22:38 +0300
From:	Faidon Liambotis <paravoid@...ian.org>
To:	Chris Wright <chrisw@...s-sol.org>
CC:	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	iommu@...ts.linux-foundation.org,
	David Woodhouse <David.Woodhouse@...el.com>
Subject: Re: [regression, bisected] fails to boot on Dell Optiplex 760 with
 VT-d enabled

Chris Wright wrote:
> AFAIK, this platform is broken when VT-d is enabled.
> Can you add this patch to a broken kernel and retest?
> Please boot with 'debug' on the kernel command line.
Thanks but David was faster, we've already established that

http://git.infradead.org/iommu-2.6.git/commit/0815565a

which is, as far as I can understand, very similar to your patch, indeed
fixes the issue.

> +	if (ver == (u32)-1 || iommu->cap == (u64)-1 || iommu->ecap == (u64)-1) {
As an observation, David's patch is checking if *both* iommu->cap and
iommu->ecap are -1, while yours checks for either. You're also checking
for ver. Obviously, I have no idea which of the two is more correct.

Thanks,
Faidon
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