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

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Message-ID: <5552EFD0.3020307@gmail.com>
Date:	Tue, 12 May 2015 23:31:44 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	"Li, ZhenHua" <zhen-hual@...com>, 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
Subject: Re: [PATCH v11 02/10] iommu/vt-d: Items required for kdump

On 05/12/2015 06:45 PM, Li, ZhenHua wrote:
> 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.

I agree with Dave.  The comment by itself makes no sense.  You would be 
better off moving this to patch 3 where you actually start to add code.

You remove the double space in patch 5 of your set so it must of 
triggered something.

Neither of these are grounds for rejecting the patches, but it is 
something you may want to clean up if you end up resubmitting.

- Alex

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