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But why is lazy_mmu_count 32 bit? Do you expect a nesting > > > level of 2^32? :) If you would reduce that to one byte you could use > > > tmy or cliy. > > > > Good point. But still, do you think it worth dropping the KASAN check? > > KASAN check for lowcore? I don't think we care - this is initialized to zero > anyway, so what could go wrong? Also given how frequently these operations are > used, yes, please drop KASAN checks. Of course you could still add an explicit KASAN/KCSAN check by adding an instrument_read() call (see e.g. s390's fpu-insn.h, which has plenty of them). But why do you think that would be helpful for a lowcore field, where it is known that is initialized to zero? What am I missing?