On Thu, 2017-02-09 at 08:28 +0530, Aneesh Kumar K.V wrote:
> In the kernel we do follow the below sequence in different code paths.
> pte = ptep_get_clear(ptep)
> ....
> set_pte_at(ptep, pte)
>
> We do that for mremap, autonuma protection update and softdirty clearing. This
> implies our optimization to skip a tlb flush when clearing a pte update is
> not valid, because for DD1 system that followup set_pte_at will be done witout
> doing the required tlbflush. Fix that by always doing the dd1 style pte update
> irrespective of new_pte value. In a later patch we will optimize the
> application
> exit case.
What about my change to set_pte_at() ? We seem to be overwriting valid PTEs,
shouldn't we deal with that ?
Cheers,
Ben.
> Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> > Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
> ---
> arch/powerpc/include/asm/book3s/64/radix.h | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/radix.h
> b/arch/powerpc/include/asm/book3s/64/radix.h
> index b4d1302387a3..70a3cdcdbe47 100644
> --- a/arch/powerpc/include/asm/book3s/64/radix.h
> +++ b/arch/powerpc/include/asm/book3s/64/radix.h
> @@ -144,16 +144,10 @@ static inline unsigned long radix__pte_update(struct
> mm_struct *mm,
> > * new value of pte
> > */
> > new_pte = (old_pte | set) & ~clr;
> > - /*
> > - * If we are trying to clear the pte, we can skip
> > - * the below sequence and batch the tlb flush. The
> > - * tlb flush batching is done by mmu gather code
> > - */
> > - if (new_pte) {
> > - asm volatile("ptesync" : : : "memory");
> > - radix__flush_tlb_pte_p9_dd1(old_pte, mm, addr);
> > + asm volatile("ptesync" : : : "memory");
> > + radix__flush_tlb_pte_p9_dd1(old_pte, mm, addr);
> > + if (new_pte)
> > __radix_pte_update(ptep, 0, new_pte);
> > - }
> > } else
> > old_pte = __radix_pte_update(ptep, clr, set);
> > asm volatile("ptesync" : : : "memory");
