On Tue, Oct 15, 2019 at 01:18:34AM +0100, Will Deacon wrote: > On Fri, Oct 11, 2019 at 10:09:35PM +0800, Jia He wrote: > > When we tested pmdk unit test vmmalloc_fork TEST1 in arm64 guest, there > > will be a double page fault in __copy_from_user_inatomic of cow_user_page. > > > > As told by Catalin: "On arm64 without hardware Access Flag, copying from > > user will fail because the pte is old and cannot be marked young. So we > > always end up with zeroed page after fork() + CoW for pfn mappings. we > > don't always have a hardware-managed access flag on arm64." > > > > -Changes > > v12: > > refine PATCH 01, remove the !! since C languages can convert unsigned > > to bool (Catalin) > > Thanks. I think it's a bit late to take something like this for 5.4 now, > especially as the current behaviour has always been there. Hopefully > somebody can queue it for 5.5 instead. I can queue this through the arm64 tree for 5.5 if I get an ack on the x86 patch (3/4) or I don't hear any complaints. -- Catalin
