linux-kernel - RE: [PATCHv3 0/6] Crashdump Accepting Active IOMMU

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Date:	Mon, 10 Mar 2014 19:10:17 +0000
From:	"Sumner, William" <bill.sumner@...com>
To:	Joerg Roedel <joro@...tes.org>
CC:	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"indou.takao@...fujitsu.com" <indou.takao@...fujitsu.com>,
	"bhe@...hat.com" <bhe@...hat.com>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ddutile@...hat.com" <ddutile@...hat.com>,
	"ishii.hironobu@...fujitsu.com" <ishii.hironobu@...fujitsu.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"Hatch, Douglas B (HPS Linux PM)" <doug.hatch@...com>,
	"Li, Zhen-Hua" <zhen-hual@...com>
Subject: RE: [PATCHv3 0/6] Crashdump Accepting Active IOMMU

Hi Joerg,

On Tue 3/4/2014 9:06 AM, Joerg Roedel wrote:
>
>On Fri, Jan 10, 2014 at 03:07:26PM -0700, Bill Sumner wrote:
>> Bill Sumner (6):
>>   Crashdump-Accepting-Active-IOMMU-Flags-and-Prototype
>>   Crashdump-Accepting-Active-IOMMU-Utility-functions
>>   Crashdump-Accepting-Active-IOMMU-Domain-Interfaces
>>   Crashdump-Accepting-Active-IOMMU-Copy-Translations
>>   Crashdump-Accepting-Active-IOMMU-Debug-Print-IOMMU
>>   Crashdump-Accepting-Active-IOMMU-Call-From-Mainline
>>
>>  drivers/iommu/intel-iommu.c | 1293
>> ++++++++++++++++++++++++++++++++++++++++---
>>  1 file changed, 1225 insertions(+), 68 deletions(-)
>
>This is a pretty big change, before merging I would like to get more eyes on it. Please make sure you get more reviews on the code and the general concept. A few things I noticed while looking at it:
Yes, as I was developing this, I realized that it is far more code than most Linux submissions.  In addition to more eyes reviewing the code, I hope to see additional members of the community trying it out -- testing it on a wide variety of system configurations.  Let me encourage additional reviewers and testers to look at this fix to crashdump.
>
>* You put a lot of code into #define CONFIG_CRASH_DUMP. Isn't the same approach necessary to for KEXEC?
Until I saw your email, I had been focused only on the immediate problem of fixing crashdump and had not considered using this approach in the more-general context of KEXEC.  It certainly looks like it could be useful with KEXEC as well.  

I would like to take-on the effort of expanding this technique into KEXEC as a separate follow-on project so that the original "fix crashdump" project is not delayed.  On a quick look, I believe that the amount of additional code would be minimal; but the expansion of the testing matrix might be quite large.
>
>* Please get rid of all the pr_debug stuff.
Will do.
>
>* I think it makes sense to put the functions to access the IOMMU
>  configuration values of the old kernel into a new file. This is better
>  than adding over 1000 new lines to intel-iommu.c
Sounds good.  I will move these functions into a new file.
>
>* I have seen your new single-patch for this change. A single patch with
>  more than 1200 changed lines is not something anyone is willing to
>  review. Please split the patches again in a meaningful and bisectable
>  way.
I will return to a multiple-patch set for future submissions.


-- Bill
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