From: Simon Guo > Sent: 27 September 2017 19:34 ... > > On X86 all the AVX registers are caller saved, the system call > > entry could issue the instruction that invalidates them all. > > Kernel code running in the context of a user process could then > > use the registers without saving them. > > It would only need to set a mark to ensure they are invalidated > > again on return to user (might be cheap enough to do anyway). > > Dunno about PPC though. > > I am not aware of any ppc instruction which can set a "mark" or provide > any high granularity flag against single or subgroup of vec regs' validity. > But ppc experts may want to correct me.
I was just thinking of a software flag. David