On Mon, Jun 26, 2017 at 09:03:18AM +1000, Balbir Singh wrote:
> On Wed, 2017-06-21 at 18:39 -0700, Ram Pai wrote:
> > Introduce set_hidx_slot() which sets the (H_PAGE_F_SECOND|H_PAGE_F_GIX)
> > bits at the appropriate location in the PTE of 4K PTE. In the
> > case of 64K PTE, it sets the bits in the second part of the PTE. Though
> > the implementation for the former just needs the slot parameter, it does
> > take some additional parameters to keep the prototype consistent.
> >
> > This function will come in handy as we work towards re-arranging the
> > bits in the later patches.
> >
> > Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx>
> > ---
> > arch/powerpc/include/asm/book3s/64/hash-4k.h | 7 +++++++
> > arch/powerpc/include/asm/book3s/64/hash-64k.h | 16 ++++++++++++++++
> > 2 files changed, 23 insertions(+)
> >
> > diff --git a/arch/powerpc/include/asm/book3s/64/hash-4k.h b/arch/powerpc/include/asm/book3s/64/hash-4k.h
> > index 9c2c8f1..cef644c 100644
> > --- a/arch/powerpc/include/asm/book3s/64/hash-4k.h
> > +++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h
> > @@ -55,6 +55,13 @@ static inline int hash__hugepd_ok(hugepd_t hpd)
> > }
> > #endif
> >
> > +static inline unsigned long set_hidx_slot(pte_t *ptep, real_pte_t rpte,
> > + unsigned int subpg_index, unsigned long slot)
> > +{
> > + return (slot << H_PAGE_F_GIX_SHIFT) &
> > + (H_PAGE_F_SECOND | H_PAGE_F_GIX);
> > +}
> > +
>
> A comment on top would help explain that 4k and 64k are different, 64k
> is a new layout.
ok.
>
> > #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >
> > static inline char *get_hpte_slot_array(pmd_t *pmdp)
> > diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
> > index 3f49941..4bac70a 100644
> > --- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
> > +++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
> > @@ -75,6 +75,22 @@ static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
> > return (pte_val(rpte.pte) >> H_PAGE_F_GIX_SHIFT) & 0xf;
> > }
> >
> > +static inline unsigned long set_hidx_slot(pte_t *ptep, real_pte_t rpte,
> > + unsigned int subpg_index, unsigned long slot)
> > +{
> > + unsigned long *hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
> > +
> > + rpte.hidx &= ~(0xfUL << (subpg_index << 2));
> > + *hidxp = rpte.hidx | (slot << (subpg_index << 2));
> > + /*
> > + * Avoid race with __real_pte()
> > + * hidx must be committed to memory before committing
> > + * the pte.
> > + */
> > + smp_wmb();
>
> Whats the other paired barrier, is it in set_pte()?
__real_pte() reads the hidx. The smp_rmb() is in that function.
>
> > + return 0x0UL;
> > +}
>
> We return 0 here and slot information for 4k pages, it is not that
> clear
We return 0 here and commit the 4k-hpte hidx.
RP
