linux-kernel - Re: [PATCH v2] intel-iommu: Disable translation if already enabled

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Date:	Tue, 23 Apr 2013 14:49:27 +0200
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,
	wei@...stanetworks.com
Subject: Re: [PATCH v2] intel-iommu: Disable translation if already enabled

On Tue, Apr 23, 2013 at 05:35:03PM +0900, Takao Indoh wrote:
> This patch disables translation(dma-remapping) before its initialization
> if it is already enabled.
> 
> This is needed for kexec/kdump boot. If dma-remapping is enabled in the
> first kernel, it need to be disabled before initializing its page table
> during second kernel boot. Wei Hu also reported that this is needed
> when second kernel boots with intel_iommu=off.
> 
> Basically iommu->gcmd is used to know whether translation is enabled or
> disabled, but it is always zero at boot time even when translation is
> enabled since iommu->gcmd is initialized without considering such a
> case. Therefor this patch synchronizes iommu->gcmd value with global
> command register when iommu structure is allocated.
> 
> Changelog:
> v2:
> - Change subject and patch description
> - Disable translation after dmar_table_init() so that it works when
>   intel_iommu=off is specified.
> 
> v1:
> https://lkml.org/lkml/2013/3/20/707
> 
> Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
> ---
>  drivers/iommu/dmar.c        |   11 ++++++++++-
>  drivers/iommu/intel-iommu.c |   15 +++++++++++++++
>  2 files changed, 25 insertions(+), 1 deletions(-)

Looks good to me, applied to x86/vt-d, thanks Takao.


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