On 02/16/2012 11:18 AM, Alexander Graf wrote: > > On 16.02.2012, at 17:58, Scott Wood wrote: > >> On 02/16/2012 04:24 AM, Alexander Graf wrote: >>> On 16.02.2012, at 10:26, Liu Yu <yu....@freescale.com> wrote: >>>> +_GLOBAL(epapr_ev_idle) >>>> +epapr_ev_idle: >>>> + rlwinm r3,r1,0,0,31-THREAD_SHIFT /* current thread_info */ >>>> + lwz r4,TI_LOCAL_FLAGS(r3) /* set napping bit */ >>>> + ori r4,r4,_TLF_NAPPING /* so when we take an exception */ >>>> + stw r4,TI_LOCAL_FLAGS(r3) /* it will return to our caller */ >>>> + >>>> + wrteei 1 >>>> + >>>> +idle_loop: >>>> + LOAD_REG_IMMEDIATE(r11, HC_VENDOR_EPAPR | HC_EV_IDLE) >>>> + >>>> +.global epapr_ev_idle_start >>>> +epapr_ev_idle_start: >>>> + li r3, -1 >>>> + nop >>>> + nop >>>> + nop >>> >>> Can't you just bl into epapr_hypercall_start? You don't even have to save >>> the old lr. because we never return anyways :) >> >> The interrupt will branch to LR, so no, we can't trash it or put it >> anywhere else. > > Hrm. But we can clobber ctr, right? So how about we make the generic version > do a bctr and then just do a small C wrapper that takes lr, moves it to ctr > and branches to the generic one?
If it's just for this, I would say don't mess with the normal hcall path for the sake of idle. If using CTR would let us get away without creating a stack frame in call sites, maybe that would be worthwhile, depending on what sort of hcalls we end up having. > Then we don't have to replicate the hypercall code all over again for every > invocation. We shouldn't need to do it for every invocation. Idle is special due to the TLF_NAPPING hack. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
