On 8/15/22 14:03, Nadav Amit wrote: >> >> At least on x86, the hardware is not supposed to do so. The only case I >> remember (and sometimes misremembers) is with KNL erratum, which perhaps >> needs to be considered: >> >> https://lore.kernel.org/all/20160708001911.9A3FD2B6@xxxxxxxxxxxxxxxxxx/ > I keep not remembering this erratum correctly. IIRC, the erratum says that > the access/dirty might be set, but it does not mean that a write is possible > after the PTE is cleared (i.e., the dirty/access might be set on the > non-present PTE, but the access itself would fail). So it is not an issue in > this case - losing A/D would not impact correctness since the access should > fail. > > Dave Hansen hates when I get confused with this one, but I cc him if he > wants to confirm. Right. The issue is strictly with the page walker setting Accessed/Dirty in a racy way. The TLB still has accurate contents at all times.
