linux-kernel - Re: [PATCH 2/2] x86/xen: Disable DMI parsing in Xen kernel.

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Date:	Thu, 28 Feb 2008 10:35:23 +0000
From:	Ian Campbell <ijc@...lion.org.uk>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mark McLoughlin <markmc@...hat.com>,
	Alexander van Heukelum <heukelum@...tmail.fm>
Subject: Re: [PATCH 2/2] x86/xen: Disable DMI parsing in Xen kernel.


On Thu, 2008-02-28 at 10:46 +0100, Ingo Molnar wrote:
> * Ian Campbell <ijc@...lion.org.uk> wrote:
> 
> > Actually scratch this patchset -- its not sufficient. For example 
> > ddcprobe in userspace causes the exact same issue vs 0xa0000.
> > 
> > Looks like the only sane solution will be to mark regions between 
> > 640K-1M reserved early on in boot.
> 
> and as luck has it, such a patch from Alexander van Heukelum has been 
> put into x86.git#testing just yesterday.
> 
> So ... could you try x86.git#testing - does it work out of box? Is the 
> reservation early enough to prevent pagetables be allocated in weird 
> places?

That patch is 64 bit only and also I'm not sure what EBDA looks like to
a Xen domU (I expect it doesn't exist). I'll give it a go but I'm not
hopeful.

>  [or am i missing something - this is about the guest kernel 
> reserving th 640k..1M area, not the host kernel - right?]

Correct, the area between 640k and 1M is just normal memory for a Xen
guest and the memory map reflects that so page tables and other stuff
get allocated in regions which would be magic data structures on native.

Ian.
-- 
Ian Campbell

The woman you buy -- and she is the least expensive -- takes a great
deal of money.  The woman who gives herself takes all your time.
		-- Balzac

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