On Thu, Jun 30, 2016 at 10:55 PM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Thu, Jun 30, 2016 at 5:12 PM, Dave Hansen <d...@sr71.net> wrote: >> >> From: Dave Hansen <dave.han...@linux.intel.com> >> >> The Intel(R) Xeon Phi(TM) Processor x200 Family (codename: Knights >> Landing) has an erratum where a processor thread setting the Accessed >> or Dirty bits may not do so atomically against its checks for the >> Present bit. This may cause a thread (which is about to page fault) >> to set A and/or D, even though the Present bit had already been >> atomically cleared. > > So I don't think your approach is wrong, but I suspect this is > overkill, and what we should instead just do is to not use the A/D > bits at all in the swap representation. > > The swap-entry representation was a bit tight on 32-bit page table > entries, but in 64-bit ones, I think we have tons of bits, don't we? > So we could decide just to not use those two bits on x86. > > It's not like anybody will ever care about 32-bit page tables on > Knights Landing anyway.
Could this affect a 32-bit guest VM? -- Brian Gerst
