Re: [PATCH] x86/mm/pat: Fix missing preemption disable for __native_flush_tlb()

[Dan Williams]

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 donât think I agree with the patch. If you call __flush_tlb_all() in a context where you might be *migrated*, then thereâs a bug. We could change the code to allow this particular use by checking that we havenât done SMP init yet, perhaps.

Hmm, are saying the entire kernel_physical_mapping_init() sequence
needs to run with pre-emption disabled?