On Sun, 9 Jun 2024 at 05:11, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Sat, 8 Jun 2024 at 13:55, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > Think of this patch mostly as a "look, adding another architecture > > isn't *that* hard - even if the constant value is spread out in the > > instructions". > > .. and here's a version that actually works. It wasn't that bad. > > Or rather, it wouldn't have been that bad had I not spent *ages* > debugging a stupid cut-and-paste error where I instead of writing > words 0..3 of the 64-bit large constant generation, wrote words 0..2 > and then overwrote word 2 (again) with the data that should have gone > into word 3. Causing the top 32 bits to be all wonky. Oops. Literally. > > That stupid typo caused like two hours of wasted time. > > But anyway, this patch actually works for me. It still doesn't do any > I$/D$ flushing, because it's not needed in practice, but it *should* > probably do that. > arm64 already has so-called 'callback' alternatives that allow the patching logic for a particular alternative sequence to be implemented by the user of the API. A callback implementation to patch a movz/movk sequence already exists, in arch/arm64/kvm/va_layout.c, used by kvm_get_kimage_voffset() and kvm_compute_final_ctr_el0().
