linux-kernel - Re: [PATCH] x86: fix init_memory

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Date:	Sat, 28 Jun 2008 22:18:24 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Yinghai Lu <yhlu.kernel@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: fix init_memory_mapping over boundary v4

Yinghai Lu wrote:
>> We should really define X_index() to return 0 for folded pagetable level X.
>>  I've had to put similar #ifdefs in other code.  Also, for the purposes of
>> making this code more unifiable, it's probably better to test for "#if
>> PAGETABLE_LEVELS >= 3" rather than for PAE specifically.
>>     
>
> does all cpu support >=3?
>   

Well, x86 32-bit PAE is 3 level, and 64-bit is 4 level; both have a 
meaningful set of pmd operations.

>
>> Is this the same as "extra = (end + PMD_SIZE + 1) & PMD_MASK"?
>>     
>
> extra = end & PMD_MASK;
> extra+ = PMD_SIZE;
>   

OK.  I wasn't sure if your intent was to round up to the next PMD_SIZE 
or add a whole new PMD_SIZE.

    J
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