linux-kernel - Re: 2.6.33-rc2: Xen/Guest switching to user mode with no user page tables

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Message-ID: <alpine.DEB.2.01.1001150011480.3483@bogon.housecafe.de>
Date:	Fri, 15 Jan 2010 00:36:42 -0800 (PST)
From:	Christian Kujau <lists@...dbynature.de>
To:	Ian Campbell <ijc@...lion.org.uk>
cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Brian Gerst <brgerst@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.33-rc2: Xen/Guest switching to user mode with no user page
 tables

On Sun, 10 Jan 2010 at 12:59, Ian Campbell wrote:
> The correct fix is for the Xen backend to declare kernel RPL == 0 for 64
> bit guests -- the hyervisor already takes care of all the necessary
> squashing to ring 3 transparently (because making the guest worry about
> it would break the very common assumption that you can distinguish user
> from kernel CS by RPL).

Yes' it's a 64bit guest, I should have mentioned this from the beginning. 
With the 2 patches from Ian and Cyrill applied, the DomU is now booting 
fine again (currently running mainline -git).

Cyrill: with your patch alone (for arch/x86/kernel/process.c), the DomU
is still not booting, Dom0 "xm dmesg" reporting the same error. As it's
working with both patches applied, should I try to test with only Ian's
patch (for arch/x86/xen/enlighten.c) applied?

In any case, feel free to add:

   Tested-by: Christian Kujau <lists@...dbynature.de>

Thanks so much for your efforts to everyone involved!

Christian.
-- 
BOFH excuse #436:

Daemon escaped from pentagram
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