linux-kernel - Re: [RFC PATCH 15/33] move segment checks to subarch

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Date:	Tue, 18 Jul 2006 12:25:33 -0700
From:	Chris Wright <chrisw@...s-sol.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Chris Wright <chrisw@...s-sol.org>, linux-kernel@...r.kernel.org,
	virtualization@...ts.osdl.org, xen-devel@...ts.xensource.com,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>,
	Zachary Amsden <zach@...are.com>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>
Subject: Re: [RFC PATCH 15/33] move segment checks to subarch

* Rusty Russell (rusty@...tcorp.com.au) wrote:
> On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
> > plain text document attachment (i386-segments)
> > We allow for the fact that the guest kernel may not run in ring 0.
> > This requires some abstraction in a few places when setting %cs or
> > checking privilege level (user vs kernel).
> 
> Zach had an alternate patch for this, which didn't assume the kernel ran
> in a compile-time known ring, but is otherwise very similar.  I've put
> it below for discussion (but Zach now tells me the asm parts are not
> required: Zach, can you mod this patch and comment?).

This patch also doesn't have a compile time known ring, it's using
get_kernel_cs() because the Xen method for booting native is dynamic and
would resolve to ring 0 in that case (XENFEAT_supervisor_mode_kernel).

> Your patch #16 finishes the job you started here, by doing the mods to
> entry.S.  I think it's cleaner to have all this in one patch (and it can
> go in almost immediately AFAICT).

I totally agree.  I actually started doing rearranging the patch order
last night and that was one of the bits that got consolidated.  It was
getting light this morning and I gave up since I was wasting lots of
time fixing patch rejects from all the rearranging, and needed a bit of
sleep before KS;-)

> Comments?
> Rusty.
> 
> Name: Kernel Ring Cleanups
> Status: Booted on 2.6.18-rc1
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

Looks fine to me, granted I haven't tried to boot it yet.  I'll double
check and report back.

thanks,
-chris
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