linux-kernel - Re: [PATCH] x86: Construct 32 bit boot time page tables in native format.

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Message-ID: <479E3B89.20101@zytor.com>
Date:	Mon, 28 Jan 2008 12:31:05 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...e.hu>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ian Campbell <ijc@...lion.org.uk>,
	Mika Penttilä <mika.penttila@...umbus.fi>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH] x86: Construct 32 bit boot time page tables in native
 format.

Rafael J. Wysocki wrote:
> On Monday, 28 of January 2008, Pavel Machek wrote:
>> Hi!
>>
>>>>>  /*
>>>>>   * Swap suspend & friends need this for resume because things like the intel-agp
>>>>>   * driver might have split up a kernel 4MB mapping.
>>>>>   */
>>>>> -char __nosavedata swsusp_pg_dir[PAGE_SIZE]
>>>>> +char swsusp_pg_dir[PAGE_SIZE]
>>>> thanks, applied.
>> Sorry, this is subtle and I've overlooked it before.
>>
>> (I thought you were only changing ifdef).
>>
>> Now you memcpy() over pg_dir when that pgdir is in use during swsusp
>> resume.
> 
> It is not.  swsusp hasn't been using swsusp_pg_dir for several months.
> Hence, the patch. :-)
> 
>> Granted, you memcpy() with same data that already are there, 
>> but it may still do some funny effects.
>>
>> Hmm, but same argument applies to lower levels of paging in 64-bit and
>> PAE cases, and we still do that memcpy-over-active-pagetables there...
>> :-(.
> 
> Actually, no.  We only do that with the kernel code mapping which should be
> safe as long as TLBs are not flushed (and they aren't).
> 

Okay... does that in any way affect using the kernel code mapping 
synchronization code to maintain a set of trampoline pagetables?

	-hpa
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