On Fri Oct 7, 2022 at 5:54 AM AEST, Segher Boessenkool wrote: > Hi! > > On Fri, Sep 23, 2022 at 01:30:04PM +1000, Nicholas Piggin wrote: > > This adds basic POWER10_CPU option, which builds with -mcpu=power10. > > > +# No prefix or pcrel > > +KBUILD_CFLAGS += $(call cc-option,-mno-prefixed) > > +KBUILD_CFLAGS += $(call cc-option,-mno-pcrel) > > Why do you disable all prefixed insns? What goes wrong if you don't?
Potentially things like kprobes. > Same question for pcrel. I'm sure you want to optimise it better, but > it's not clear to me how it fails now? For pcrel addressing? Bootstrapping the C environment is one, the module dynamic linker is another. Some details in this series. https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-September/248521.html > > Please say in the comment what is wrong, don't spread fear :-) > > > +# No AltiVec or VSX or MMA instructions when building kernel > > KBUILD_CFLAGS += $(call cc-option,-mno-altivec) > > KBUILD_CFLAGS += $(call cc-option,-mno-vsx) > > +KBUILD_CFLAGS += $(call cc-option,-mno-mma) > > MMA code is never generated unless the code asks for it explicitly. > This is fundamental, not just an implementations side effect. Well, now it double won't be generated :) Thanks, Nick
