linux-kernel - Re: [PATCH retry] intel-iommu:make identity

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Message-ID: <1320140052.2089.5.camel@shinybook.infradead.org>
Date:	Tue, 01 Nov 2011 10:34:10 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Dave Young <dyoung@...hat.com>
Cc:	kexec@...ts.infradead.org, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, vgoyal@...hat.com,
	horms@...ge.net.au, luyu@...hat.com
Subject: Re: [PATCH retry] intel-iommu:make identity_map default for crash
 dump

On Tue, 2011-11-01 at 17:19 +0800, Dave Young wrote:
> kdump kernel sometimes will get DMAR faults which
> is caused by random in-flight dma from 1st kernel
> 
> Here make the identity_mapping as default for this case

So you want to *allow* the random in-flight DMA? And with an identity
mapping it's really going to random addresses, since it'll be
untranslated and won't even go to the physical addresses which it was
originally intended for?

This seems entirely broken to me.

If there is "random in-flight dma" from the first kernel, the correct
thing to do is *block* it. Which is what we do.

-- 
dwmw2

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