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

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Message-ID: <20100812170644.GZ23755@8bytes.org>
Date:	Thu, 12 Aug 2010 19:06:44 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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 Thu, Aug 12, 2010 at 08:34:37AM -0700, H. Peter Anvin wrote:

> 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...

Great.

The synchronization problem might be real. The cpu_init function uses
per-cpu variables which might not be present in the early synced
tramponline page table (iirc). The change to swapper_pg_dir and the
global tlb flush should probably be moved to the very beginning of the
start_secondary function.

	Joerg

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