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SubjectRe: [RFC PATCH 15/33] move segment checks to subarch
* Rusty Russell ( 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 <>

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

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