> I'm not sure that works on processes before power8. > > There DSCR SPR number 0x11 will always trap and emulate from userspace > (see arch/powerpc/kernel/traps.c:emulate_instruction()). That is not > controlled by FSCR and should work on POWER7 where FSCR is not > present. We need to set the inherit bit there too. > > DSCR SPR number 0x3 is controlled by fscr, but it's only avaliable on > POWER8. > >> Right now the FSCR switch is conditional on FTR_ARCH_207S which is >> more exclusive than FTR_DSCR, but I guess the actual FSCR register is >> universal to PPC64 like the fscr field in the thread struct? If so, I >> can just move the FSCR save/restore out of the 207 conditional. > > FSCR was only introduced in power8, so it needs to be 207 conditional >
So on P6/P7 (which have FTR_DSCR) set we're potentially mtspr'ing to a non-existent register? Yuck. Can at least strip that logic out thanks to the full context switch, I think, even if dscr_inherit actually has a use. - Jack _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
