linux-kernel - Re: intel-iommu: CONFIG

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Message-ID: <20080507205818.GA15746@linux.intel.com>
Date:	Wed, 7 May 2008 13:58:18 -0700
From:	mark gross <mgross@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Gabriel C <nix.or.die@...glemail.com>,
	linux-kernel@...r.kernel.org, ashok.raj@...el.com,
	shaohua.li@...el.com, anil.s.keshavamurthy@...el.com,
	jbarnes@...tuousgeek.org, linux-pci@...ey.karlin.mff.cuni.cz
Subject: Re: intel-iommu: CONFIG_DMAR*=y kills my box

On Tue, May 06, 2008 at 01:15:54PM -0700, Andrew Morton wrote:
> On Wed, 30 Apr 2008 01:04:45 +0200
> Gabriel C <nix.or.die@...glemail.com> wrote:
> >
> 
> Guys, it's really painful having to scroll through thousand-line emails to
> find a few lines of information.  Please trim stuff.

sorry.  I will next time.
 
> > 
> > > 
> > > I do find it quite odd that a DMA code path specific to PCIE is somehow
> > > in the loop for a parallel port device.  Should this be possible?
> > 
> > I have no idea =) ( PCI folks added to CC )
> > 
> > > 
> > > I could easily be wrong so feel free to correct me but;
> > > I think your bios is goofy / unprepared to support IOMMU / VT-d and
> > > doing strange things with enumerated a parallel port on a PCIE bus with
> > > VTD is turned on...
> > 
> > I will contact ASUS peoples about the BIOS but it has for sure VT-d support and it is enabled.
> 
> So..  what happened here?  It seems like a pretty fatal problem, and
> personally I don't think that contacting vendors about BIOS upgrades is a
> suitable general solution.  It would be much better to find a kernel-based
> fix or workaround?
> 

We don't have a stable work around yet.  Unwrapping the IOMMU startup
code is proving tricky.  The only thing I can think of is to change the
polarity of the intel-iommu command line to default to off, and if your
bios doesn't suck you can enable it if you want to use it.

I don't like this option much, since all the issues have been bios
based.  But, I don't know what else to do at this time.

--mgross

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