On Wed, Dec 16, 2020 at 09:40:59AM +0100, Peter Zijlstra wrote: > > So much algorithm. > > :-) > > It's not really hard, but it has a few pesky details (as always). It really hurt my brain to look at it. > > Could we make it easier by caching the shared > > per-alt-group CFI state somewhere along the way? > > Yes, but when I tried it grew the code required. Runtime costs would be > less, but I figured that since alternatives are typically few and small, > that wasn't a real consideration. Aren't alternatives going to be everywhere now with paravirt using them? > That is, it would basically cache the results of find_alt_unwind(), but > you still need find_alt_unwind() to generate that data, and so you gain > the code for filling and using the extra data structure. > > Yes, computing it 3 times is naf, but meh. Haha, I loved this sentence. > > Thoughts? This is all theoretical of course, I could try to do a patch > > tomorrow. > > No real objection, I just didn't do it because 1) it works, and 2) even > moar lines. I'm kind of surprised it would need moar lines. Let me play around with it and maybe I'll come around ;-) -- Josh
