Re: [XenPPC] performance profiling current and future steps

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Mar 26, 2007, at 8:26 AM, Christian Ehrhardt wrote:

> Jimi Xenidis wrote:
> > On Mar 23, 2007, at 9:07 AM, Hollis Blanchard wrote:
> > > Right, that won't fit in EXCEPTION_HEAD (you will get the assembler
> > > error messages Jimi pasted above).
> > Yeah,
> > So EXCEPTION_HEAD branches to a passed in label. Find all those  
> > labels and insert PMU_SAVE_STATE there.
> I need a register to clobber with my "ori". (H_) 
> EXCEPTION_SAVE_STATE clobbers r0 anyway and it resides in all  
> continue labels that are passed to EXCEPTION_HEAD. So  
> PMU_SAVE_STATE can follow in its wake and clobber r0 too like  
> EXCEPTION_SAVE_STATE.
> branches to EXCEPTION_HEAD:
>        xenppc-unstable_step1/xen# cat arch/powerpc/powerpc64/ 
> exceptions.S | grep "EXCEPTION_HEAD" | sort | uniq
>            EXCEPTION_HEAD r13 ex_dec_continued
>            EXCEPTION_HEAD r13 ex_external_continued
>            EXCEPTION_HEAD r13 ex_hcall_continued
>            EXCEPTION_HEAD r13 ex_hdec_continued
>            EXCEPTION_HEAD r13 ex_machcheck_continued
>            EXCEPTION_HEAD r13 ex_program_continued
>
>
>
> One of those calls as example "diff -Naur":
> @@ -384,6 +391,7 @@
>     mr r14, r0
>     EXCEPTION_SAVE_STATE r1
> +    PMU_SAVE_STATE r0,r0
>     mr r4, r14
>     LOADADDR r12, program_exception
>     mr r3, r1                           /* pass pointer to  
> cpu_user_regs */
> Please correct me If my assumption is wrong that I'm allowed to  
> clobber r0 there.
After EXCEPTION_SAVE_STATE r0 and r3-r12 are fair game, so yeah, r0  
is fine.
r1 points to your save area so I'd use "PMU_SAVE_STATE r0, r1", the  
macro does not save any state, but it will one day.
You should also from the second argument (r1) until you have a patch  
that actually needs it.
-JX

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