Re: [Xen-ia64-devel][PATCH] optimize entry and exit path

[Al Stone <ahs3@xxxxxxxxx>]

On Mon, 2006-07-10 at 15:24 +0800, Xu, Anthony wrote:
> VMM save/restore r4~r7 and unat to handle virtualization fault and mmio 
> access,
> but it is not necessary for other faults to save/restore these registers.
> This patch is to save/restore these registers only when dtlb and 
> virtualization fault happen.

If I understand this patch correctly, and I'm not sure I do, so please
bear with me, it looks like I now have two entry points into the same
block of code -- GLOBAL_ENTRY(ia64_leave_hypervisor_prepare) and a few
instructions later, GLOBAL_ENTRY(ia64_leave_hypervisor).  That makes
sense if the goal is to shave off some instructions that are not always
necessary.  I've used that trick many times myself.

What puzzles me, though, is what happens to the unwind info?  Without
an END for ia64_leave_hypervisor_prepare, am I losing unwind info, or
possibly confusing the info for ia64_leave_hypervisor?  Or am I just
not seeing something obvious?

I'm still trying to grok Xen, so be gentle :)...

-- 
Ciao,
al
----------------------------------------------------------------------
Al Stone                                      Alter Ego:
Open Source and Linux R&D                     Debian Developer
Hewlett-Packard Company                       http://www.debian.org
E-mail: ahs3@xxxxxxxxx                        ahs3@xxxxxxxxxx
----------------------------------------------------------------------


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