On Tue, Jan 12, 2021 at 02:29:51PM -0800, Nadav Amit wrote: > > On Jan 12, 2021, at 1:43 PM, Will Deacon <will@xxxxxxxxxx> wrote: > > > > On Tue, Jan 12, 2021 at 12:38:34PM -0800, Nadav Amit wrote: > >>> On Jan 12, 2021, at 11:56 AM, Yu Zhao <yuzhao@xxxxxxxxxx> wrote: > >>> On Tue, Jan 12, 2021 at 11:15:43AM -0800, Nadav Amit wrote: > >>>> I will send an RFC soon for per-table deferred TLB flushes tracking. > >>>> The basic idea is to save a generation in the page-struct that tracks > >>>> when deferred PTE change took place, and track whenever a TLB flush > >>>> completed. In addition, other users - such as mprotect - would use > >>>> the tlb_gather interface. > >>>> > >>>> Unfortunately, due to limited space in page-struct this would only > >>>> be possible for 64-bit (and my implementation is only for x86-64). > >>> > >>> I don't want to discourage you but I don't think this would end up > >>> well. PPC doesn't necessarily follow one-page-struct-per-table rule, > >>> and I've run into problems with this before while trying to do > >>> something similar. > >> > >> Discourage, discourage. Better now than later. > >> > >> It will be relatively easy to extend the scheme to be per-VMA instead of > >> per-table for architectures that prefer it this way. It does require > >> TLB-generation tracking though, which Andy only implemented for x86, so I > >> will focus on x86-64 right now. > > > > Can you remind me of what we're missing on arm64 in this area, please? I'm > > happy to help get this up and running once you have something I can build > > on. > > Let me first finish making something that we can use as a basis for a > discussion. I do not waste your time before I have something ready. Sure thing! Give me a shout when you're ready. Will
