linux-kernel - Re: [PATCH] intel-iommu: Synchronize gcmd value with global command register

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Message-ID: <20130327103122.GK30540@8bytes.org>
Date:	Wed, 27 Mar 2013 11:31:22 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Takao Indoh <indou.takao@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	dwmw2@...radead.org, kexec@...ts.infradead.org
Subject: Re: [PATCH] intel-iommu: Synchronize gcmd value with global command
 register

On Wed, Mar 27, 2013 at 02:02:44PM +0900, Takao Indoh wrote:
> The root cause of this problem is mismatch between iommu->gcmd and
> global command register in the case of kdump. At boot time, initial
> value of iommu->gcmd is zero as I wrote above, but actual global command
> register is *not* zero because some bits like IRE/TE/QIE are already set
> in *first* kernel. Therefore this patch synchronize them to fix this
> problem.

Ok, I understand, but I still don't see why this is a problem. There is
no point for the kdump kernel to preserve hardware state from the
previous kernel. So I think the way it is implemented is correct.


	Joerg


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