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Date: Tue, 2 Apr 2013 16:05:47 +0200
From: Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH] intel-iommu: Synchronize gcmd value with global command
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To: Takao Indoh <indou.takao@jp.fujitsu.com>
Cc: kexec@lists.infradead.org, iommu@lists.linux-foundation.org, dwmw2@infradead.org, linux-kernel@vger.kernel.org

On Mon, Apr 01, 2013 at 02:45:18PM +0900, Takao Indoh wrote:
> <Current flow on kdump boot>
> enable_IR
>   intel_enable_irq_remapping
>     iommu_disable_irq_remapping  <== IRES/QIES/TES disabled here
>     dmar_disable_qi              <== do nothing
>     dmar_enable_qi               <== QIES enabled
>     intel_setup_irq_remapping    <== IRES enabled

But what we want to do here in the kdumo case is to disable translation
too, right? Because the former kernel might have translation and
irq-remapping enabled and the kdump kernel might be compiled without
support for dma-remapping. So if we don't disable translation here too
the kdump kernel is unable to do DMA.

I agree that disabling translation should be a bit more explicit instead
of the current code.


	Joerg



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