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

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Message-ID: <4C64148D.5080305@zytor.com>
Date:	Thu, 12 Aug 2010 08:34:37 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Joerg Roedel <joro@...tes.org>
CC:	"Roedel, Joerg" <Joerg.Roedel@....com>,
	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 08/12/2010 07:41 AM, Joerg Roedel wrote:
> On Thu, Aug 05, 2010 at 07:14:14AM -0700, H. Peter Anvin wrote:
>> On 08/05/2010 12:45 AM, Roedel, Joerg wrote:
>> 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.
> 
> Yeah, We could probably use the same symbol names for the trampoline and
> the swapper page-table on 32 and 64 bit and merge the code that handles
> it between the architectures. Shouldn't be too difficult. We cook
> something up :-)
> But do you mind to take this patch first? It fixes the occurence of an
> erratum on AMD hardware, it is a quite simple fix compared to the rework
> suggested. In fact, I would like to have a simple patch to fix the
> problem first (and backport it as necessary) and then go the way to
> rework the current code differences between 32 and 64 bit.
> 

Agreed.  I do have a concern about the kernel page tables not being
synchronized into trampoline_pg_dir (it's only an issue for 32-bit
!PAE), so at the very least we need to keep an eye out for it...

	-hpa

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

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