Hi, Did you get a chance to look at these? This first patch 1/11 solves the lockup problem that Guenter reported with my changes to core mm code. So I plan to resubmit my patches to Andrew's -mm tree with this patch to avoid nios2 breakage. Thanks, Nick On Mon, 24 Sep 2018 01:08:20 +1000 Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > Fault paths like do_read_fault will install a Linux pte with the young > bit clear. The CPU will fault again because the TLB has not been > updated, this time a valid pte exists so handle_pte_fault will just > set the young bit with ptep_set_access_flags, which flushes the TLB. > > The TLB is flushed so the next attempt will go to the fast TLB handler > which loads the TLB with the new Linux pte. The access then proceeds. > > This design is fragile to depend on the young bit being clear after > the initial Linux fault. A proposed core mm change to immediately set > the young bit upon such a fault, results in ptep_set_access_flags not > flushing the TLB because it finds no change to the pte. The spurious > fault fix path only flushes the TLB if the access was a store. If it > was a load, then this results in an infinite loop of page faults. > > This change adds a TLB flush in update_mmu_cache, which removes that > TLB entry upon the first fault. This will cause the fast TLB handler > to load the new pte and avoid the Linux page fault entirely. > > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> > --- > arch/nios2/mm/cacheflush.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/nios2/mm/cacheflush.c b/arch/nios2/mm/cacheflush.c > index 506f6e1c86d5..d58e7e80dc0d 100644 > --- a/arch/nios2/mm/cacheflush.c > +++ b/arch/nios2/mm/cacheflush.c > @@ -204,6 +204,8 @@ void update_mmu_cache(struct vm_area_struct *vma, > struct page *page; > struct address_space *mapping; > > + flush_tlb_page(vma, address); > + > if (!pfn_valid(pfn)) > return; > > -- > 2.18.0 >
