linux-kernel - Re: How could we get rid of saved_max

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Date:	Wed, 05 Mar 2014 22:50:41 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Muli Ben-Yehuda <muli@...technion.ac.il>,
	WANG Chao <chaowang@...hat.com>
CC:	"Jon D. Mason" <jdmason@...zu.us>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vivek Goyal <vgoyal@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>, Baoquan He <bhe@...hat.com>,
	kexec@...ts.infradead.org, discuss@...-64.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: How could we get rid of saved_max_pfn for calgary iommu?

On 03/05/2014 10:47 PM, Muli Ben-Yehuda wrote:
> On Wed, Mar 05, 2014 at 01:36:17PM +0800, WANG Chao wrote:
> 
>> Hi, Muli
>>
>> saved_max_pfn is becoming a setback for kexec-tools. Ideally calgary
>> could get rid of saved_max_pfn at all. But If this can't work, how
>> about exporting a calgary tce table size to user space, so that
>> kexec-tools can simply pass calgary=xxx cmdline to 2nd kernel.
> 
> As Jon noted, this code is used to so that the TCE table remains
> consistent between the original and the kexec'd kernel. I see two
> options: either we hard code the TCE table size to the max so that
> this bit of code becomes redundant, or we explicitly pass the original
> table size (or the original max_pfn) to the kexec'd kernel. The first
> option is more appealing, because I don't think anyone is actually
> using the TCE table size -- we mostly added it for debugging the IOMMU
> TCE code at the time -- but since I don't have a Calgary machine
> anymore, I don't have any way to test it. The second option is uglier
> but would be fully backward-compatible and less likely to break
> things. Given that very few people are likely running the latest
> upstream kernel on Calgary/CalIOC2 machines, I'm inclined towards the
> first option.
> 
>> BTW MAINTAINERS file still uses your old email, please update
>> accordingly.
> 
> I think you are the first person to actually look up the Calgary
> maintainers in the last few years :-)
> 

OK, second question... is it time to axe Calgary?

	-hpa


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