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Passing an address and reusing the existing set_memory_ro() >> definitely makes things simpler. >> >> However, there is an arm64 specific limitation: >> currently, the set_memory_r* api on arm64 only support the vmap >> region and do not handle linear map addresses. >> >> If we go this route, should I extend the arm64 set_memory_r* >> implementation in the next version? The plan would be to make it check >> for the bblm2 feature and modify the linear map PTEs accordingly. >> What do you think? > Good point! It's not really clear on which ranges set_memory*() is supposed to > work ... > > arm64 only works on vmalloc/vmap, x86 and riscv on ordinary directmap ... what a > mess. arm64 version works on vmalloc/vmap *and* the linear map alias if rodata is on (a.k.a. full before). It should be not hard to make it work for linear map address (w/o vmalloc/vmap alias). I think we can just follow riscv's implementation by doing: if (vmalloc or vmap address)     ... else if (linear map address)     ... Thanks, Yang > > Having a new direct-map specific function with clear semantics might indeed > avoid even messing with that. > > So, yeah, given that we have > > set_direct_map_invalid_noflush > set_direct_map_default_noflush > set_direct_map_valid_noflush > > Let's add a > > set_direct_map_ro() > > Or (my preference) > > change_direct_map_ro() > > But given the existing naming scheme ... maybe just set_direct_map_ro() and > we'll clean this up another day. > > > Now, should there also be a "_noflush" in there, or who is supposed to flush the > TLB (or don't we flush at all, because it's used early during boot so far)? > > In any case, for this function we should add excessive documentation and define > clear semantics. >