linux-kernel - Re: [PATCH 1/2] x86-32: Fix crashes with CPU hotplug on AMD machines

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Date:	Thu, 05 Aug 2010 07:14:14 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Roedel, Joerg" <Joerg.Roedel@....com>
CC:	Borislav Petkov <bp@...64.org>, "mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Herrmann3, Andreas" <Andreas.Herrmann3@....com>,
	"Seidel, Conny" <Conny.Seidel@....com>,
	"Sarathy, Bhavna" <Bhavna.Sarathy@....com>,
	"greg@...ah.com" <greg@...ah.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86-32: Fix crashes with CPU hotplug on AMD machines

On 08/05/2010 12:45 AM, Roedel, Joerg wrote:
> 
> To make sure I understand correctly, you suggest to initialize
> tramponline_pg_dir in the boot sequence of the first cpu and fork
> swapper_pg_dir from it later on?
> 

Correct.

>> I realize this isn't how the 64-bit code works at the moment, but in a
>> lot of ways I think it would be better if it did.
> 
> Yeah, may make sense. This patch already brings the 32 bit
> implementation closer to the 64 bit one. On 64 bit things are somewhat
> simpler because the tramponline page table can be defined at
> compile-time there (contains only 2 pgd_t entries) while on 32 bit we
> have to initialize it at runtime.

Correct, again.  It's unclear to me if we can get away with the very
simple 64-bit approach -- in particular, not including all the 1:1
mappings in the kernel -- for all future users, though.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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