Re: [XenPPC] performance profiling current and future steps

[Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>]

Jimi Xenidis wrote:
...
> > Ensure MMCR0[FCH] for this first step:
> > -(ensure) set MMCR[FCH] always in xen when entering xen space. This 
> > should prevent a domain
> >  messing up MMCR0[FCH]
> > ->EXCEPTION_HEAD in exception.S set MMCR0[FCH] always
> You need at least the following instructions:
>     mfspr r0, SPRN_MMCR0
>     ori r0, r0, 1 /* MMRC0_FCH */
>     mtspr 795, SPRN_MMCR0
>
> Unfortuantely, there is not enough room in EXCEPTION_HEAD for that and 
> you will get:
>   exceptions.S: Assembler messages:
>   exceptions.S:246: Error: attempt to .org/.space backwards? (-4)
>   exceptions.S:253: Error: attempt to .org/.space backwards? (-4)
>   exceptions.S:260: Error: attempt to .org/.space backwards? (-4)
>   exceptions.S:267: Error: attempt to .org/.space backwards? (-4)
>   exceptions.o: Bad value
>   exceptions.S:626: FATAL: Can't write exceptions.o: Bad value
>
>
> I suggest we start a new macro PMU_SAVE_STATE(save,scratch), which 
> does the above (for now, using only scratch) and sprinkling it in all 
> the code that EXCEPTION_HEAD branches to.
Yep, I had those already:
        mfspr r0,SPRN_MMCR0             /* ensure MMCR0[FCH]=1 */
        ori r0,r0,MMCR0_FCH
        mtspr SPRN_MMCR0, r0

Do you mean to insert a branch to PMU_SAVE_STATE from EXCEPTION_HEAD or 
to put a PMU_SAVE_STATE branch to every section calling EXCEPTION_HEAD ?
Can someone please point at a code piece that does a similar macro 
definition and branch already.
Alternatively we could setup an "assist" session with screen -x 
developing this part together if there is a volunteer.
I created this one blindly now as a start

    .macro PMU_SAVE_STATE save scratch
        mfspr \scratch,SPRN_MMCR0             /* ensure MMCR0[FCH]=1, 
not yet saving anything */
        ori \scratch,\scratch,MMCR0_FCH
        mtspr SPRN_MMCR0, \scratch
    .endm

and added the following to EXCEPTION_HEAD, but I guess it it wrong that 
way ;)
    PMU_SAVE_STATE r0 r0

--

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
Ehrhardt@xxxxxxxxxxxxxxxxxxx
Ehrhardt@xxxxxxxxxx

IBM Deutschland Entwicklung GmbH
Vorsitzender des Aufsichtsrats: Johann Weihen 
Geschäftsführung: Herbert Kircher 
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294


_______________________________________________
Xen-ppc-devel mailing list
Xen-ppc-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ppc-devel