linux-kernel - Re: [PATCH] Fix VMI crash on boot in 2.6.27+ kernels

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Message-Id: <1228894281.8766.22.camel@bodhitayantram.eng.vmware.com>
Date:	Tue, 09 Dec 2008 23:31:21 -0800
From:	Zachary Amsden <zach@...are.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, Huang Ying <ying.huang@...el.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"norman@...backs.co.uk" <norman@...backs.co.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Alok Kataria <alokkataria1@...il.com>,
	Bruno Prémont <"bruno .premont"@restena.lu>,
	"xl@...igned.net" <xl@...igned.net>,
	"dsd@...too.org" <dsd@...too.org>
Subject: Re: [PATCH] Fix VMI crash on boot in 2.6.27+ kernels

     A. On Tue, 2008-12-09 at 17:48 -0800, H. Peter Anvin wrote:
> Yinghai Lu wrote:
> > 
> > VMI initialiation can relocate the fixmap, causing early_ioremap
> > to malfunction if it is initialized before the relocation.  The
> > ioremap area is low enough in virtual address space that no actual
> > collision occurs, however, because the pagetables for it were not
> > allocated under VMI mode, the pagetable updates are dropped by
> > the hypervisor as irrelevant, resulting in a crash on boot.
> > 
> 
> I have mentioned in the past that I think the very concept of relocating
> the fixmap to be utterly braindead.  Instead, I believe we should locate
> it low in kernel space so it doesn't have to be relocated.  It's
> unfortunately a relatively large change.

I agree, but a bit too late for 2.6.27 stable and 2.6.28-rc.

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