[ added Kirill ] On Sat, Nov 10, 2018 at 4:19 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > On Nov 10, 2018, at 3:57 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > >> On Fri, Nov 9, 2018 at 4:22 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > >> > >> > >> > >>> On Nov 9, 2018, at 4:05 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > >>> > >>> Commit f77084d96355 "x86/mm/pat: Disable preemption around > >>> __flush_tlb_all()" addressed a case where __flush_tlb_all() is called > >>> without preemption being disabled. It also left a warning to catch other > >>> cases where preemption is not disabled. That warning triggers for the > >>> memory hotplug path which is also used for persistent memory enabling: > >> > >> I don’t think I agree with the patch. If you call __flush_tlb_all() in a context where you might be *migrated*, then there’s a bug. We could change the code to allow this particular use by checking that we haven’t done SMP init yet, perhaps. > > > > Hmm, are saying the entire kernel_physical_mapping_init() sequence > > needs to run with pre-emption disabled? > > If it indeed can run late in boot or after boot, then it sure looks buggy. Either the __flush_tlb_all() should be removed or it should be replaced with flush_tlb_kernel_range(). It’s unclear to me why a flush is needed at all, but if it’s needed, surely all CPUs need flushing. Yeah, I don't think __flush_tlb_all() is needed at kernel_physical_mapping_init() time, and at kernel_physical_mapping_remove() time we do a full flush_tlb_all(). Kirill?
