On Fri, Aug 24, 2018 at 10:26:50AM -0700, Nadav Amit wrote: > at 1:47 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > On Thu, Aug 23, 2018 at 02:39:59PM +0100, Will Deacon wrote: > >> The only problem with this approach is that we've lost track of the granule > >> size by the point we get to the tlb_flush(), so we can't adjust the stride of > >> the TLB invalidations for huge mappings, which actually works nicely in the > >> synchronous case (e.g. we perform a single invalidation for a 2MB mapping, > >> rather than iterating over it at a 4k granule). > >> > >> One thing we could do is switch to synchronous mode if we detect a change in > >> granule (i.e. treat it like a batch failure). > > > > We could use tlb_start_vma() to track that, I think. Shouldn't be too > > hard. > > Somewhat unrelated, but I use this opportunity that TLB got your attention > for something that bothers me for some time. clear_fixmap(), which is used > in various places (e.g., text_poke()), ends up in doing only a local TLB > flush (in __set_pte_vaddr()). > > Is that sufficient? Urgh.. weren't the fixmaps per cpu? Bah, I remember looking at this during PTI, but I seem to have forgotten everything again.
