On Tue, 2017-08-29 at 13:27 +0200, Peter Zijlstra wrote: > mpe helped me out and explained that is the PWC hint to TBLIE. > > So, you set need_flush_all when you unhook pud/pmd/pte which you then > use to set PWC. So free_pgtables() will do the PWC when it unhooks > higher level pages. > > But you're right that there's some issues, free_pgtables() itself > doesn't seem to use mm->page_table_lock,pmd->lock _AT_ALL_ to unhook the > pages. > > If it were to do that, things should work fine since those locks would > then serialize against the speculative faults, we would never install a > page if the VMA would be under tear-down and it would thus not be > visible to your caches either. That's one case. I don't remember of *all* the cases to be honest, but I do remember several times over the past few years thinking "ah we are fine because the mm sem taken for writing protects us from any concurrent tree structure change" :-) Cheers, Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
