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

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

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.

Signed-off-by: Anthony Xu < anthony.xu@xxxxxxxxx>

>-----Original Message-----
>From: Al Stone [mailto:ahs3@xxxxxxxxx]
>Sent: 2006?7?11? 5:07
>To: Xu, Anthony
>Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-ia64-devel][PATCH] optimize entry and exit path
>
>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
>----------------------------------------------------------------------

Attachment: entry_exit_path_optimize2.patch
Description: entry_exit_path_optimize2.patch

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