> On Jan 12, 2021, at 2:29 PM, Nadav Amit <nadav.amit@xxxxxxxxx> 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. If you want a hand, let me know. I suspect you understand the x86 code as well as I do at this point, though :)
