linux-kernel - Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump

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Date:	Wed, 13 May 2015 09:45:29 +0800
From:	"Li, ZhenHua" <zhen-hual@...com>
To:	Dave Young <dyoung@...hat.com>
CC:	dwmw2@...radead.org, indou.takao@...fujitsu.com, bhe@...hat.com,
	joro@...tes.org, vgoyal@...hat.com,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, jerry.hoemann@...com, tom.vaden@...com,
	li.zhang6@...com, lisa.mitchell@...com, billsumnerlinux@...il.com,
	rwright@...com, "Li, ZhenHua" <zhen-hual@...com>
Subject: Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump

On 05/12/2015 04:17 PM, Dave Young wrote:
> On 05/11/15 at 05:52pm, Li, Zhen-Hua wrote:
>> Add context entry functions needed for kdump.
>> +/*
>> + * Fix Crashdump failure caused by leftover DMA through a hardware IOMMU
>> + *
>> + * Fixes the crashdump kernel to deal with an active iommu and legacy
>> + * DMA from the (old) panicked kernel in a manner similar to how legacy
>> + * DMA is handled when no hardware iommu was in use by the old kernel --
>> + * allow the legacy DMA to continue into its current buffers.
>> + *
>> + * In the crashdump kernel, this code:
>> + * 1. skips disabling the IOMMU's translating.
>> + * 2. Do not re-enable IOMMU's translating.
>> + * 3. In kdump kernel, use the old root entry table.
>> + * 4. Allocate pages for new context entry, copy data from old context entries
>> + *    in the old kernel to the new ones.
>> + *
>> + * In other kinds of kernel, for example, a kernel started by kexec,
>> + * do the same thing as crashdump kernel.
>> + */
>> +
>> +
>
> Above comments should come along with the code changes instead of putting it
> in this patch.
>
> BTW, there's one more blank line at the end..
Code change is in 00/10, the cover letter.
And the blank does not matter, I checked the patch with 
scripts/checkpatch.pl,  no warnings, no errors.


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