On Tue, May 23, 2017 at 8:40 PM, Balbir Singh [off-list ref] wrote:

On Tue, May 23, 2017 at 2:05 PM, Oliver O'Halloran [off-list ref] wrote:

quoted

Add support for the devmap bit on PTEs and PMDs for PPC64 Book3S.  This
is used to differentiate device backed memory from transparent huge
pages since they are handled in more or less the same manner by the core
mm code.

Cc: Aneesh Kumar K.V <redacted>
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
---
v1 -> v2: Properly differentiate THP and PMD Devmap entries. The
mm core assumes that pmd_trans_huge() and pmd_devmap() are mutually
exclusive and v1 had pmd_trans_huge() being true on a devmap pmd.

Aneesh, this has been fleshed out substantially since v1. Can you
re-review it? Also no explicit gup support is required in this patch
since devmap support was added generic GUP as a part of making x86 use
the generic version.
---
 arch/powerpc/include/asm/book3s/64/hash-64k.h |  2 +-
 arch/powerpc/include/asm/book3s/64/pgtable.h  | 37 ++++++++++++++++++++++++++-
 arch/powerpc/include/asm/book3s/64/radix.h    |  2 +-
 arch/powerpc/mm/hugetlbpage.c                 |  2 +-
 arch/powerpc/mm/pgtable-book3s64.c            |  4 +--
 arch/powerpc/mm/pgtable-hash64.c              |  4 ++-
 arch/powerpc/mm/pgtable-radix.c               |  3 ++-
 arch/powerpc/mm/pgtable_64.c                  |  2 +-
 8 files changed, 47 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 9732837aaae8..eaaf613c5347 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h

@@ -180,7 +180,7 @@ static inline void mark_hpte_slot_valid(unsigned char *hpte_slot_array,
  */
 static inline int hash__pmd_trans_huge(pmd_t pmd)
 {
-       return !!((pmd_val(pmd) & (_PAGE_PTE | H_PAGE_THP_HUGE)) ==
+       return !!((pmd_val(pmd) & (_PAGE_PTE | H_PAGE_THP_HUGE | _PAGE_DEVMAP)) ==
                  (_PAGE_PTE | H_PAGE_THP_HUGE));
 }

Like Aneesh suggested, I think we can probably skip this check here

quoted

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 85bc9875c3be..24634e92dd0b 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -79,6 +79,9 @@

 #define _PAGE_SOFT_DIRTY       _RPAGE_SW3 /* software: software dirty tracking */
 #define _PAGE_SPECIAL          _RPAGE_SW2 /* software: special page */
+#define _PAGE_DEVMAP           _RPAGE_SW1
+#define __HAVE_ARCH_PTE_DEVMAP
+
 /*
  * Drivers request for cache inhibited pte mapping using _PAGE_NO_CACHE
  * Instead of fixing all of them, add an alternate define which

@@ -599,6 +602,16 @@ static inline pte_t pte_mkhuge(pte_t pte)
        return pte;
 }

+static inline pte_t pte_mkdevmap(pte_t pte)
+{
+       return __pte(pte_val(pte) | _PAGE_SPECIAL|_PAGE_DEVMAP);
+}
+
+static inline int pte_devmap(pte_t pte)
+{
+       return !!(pte_raw(pte) & cpu_to_be64(_PAGE_DEVMAP));
+}
+
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
        /* FIXME!! check whether this need to be a conditional */

@@ -963,6 +976,9 @@ static inline pte_t *pmdp_ptep(pmd_t *pmd)
 #define pmd_mk_savedwrite(pmd) pte_pmd(pte_mk_savedwrite(pmd_pte(pmd)))
 #define pmd_clear_savedwrite(pmd)      pte_pmd(pte_clear_savedwrite(pmd_pte(pmd)))

+#define pud_pfn(...) (0)
+#define pgd_pfn(...) (0)
+

Don't get these bits.. why are they zero?

I think that was just hacking stuff until it worked. pud_pfn() needs
to exist for the kernel to build when __HAVE_ARCH_PTE_DEVMAP is set,
but we don't need it to do anything (yet) since pud_pfn() is only used
for handing devmap PUD faults. We currently support those so we will
never hit that code path. pgd_pfn() can die though.

quoted

 #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 #define pmd_soft_dirty(pmd)    pte_soft_dirty(pmd_pte(pmd))
 #define pmd_mksoft_dirty(pmd)  pte_pmd(pte_mksoft_dirty(pmd_pte(pmd)))

@@ -1137,7 +1153,6 @@ static inline int pmd_move_must_withdraw(struct spinlock *new_pmd_ptl,
        return true;
 }

-
 #define arch_needs_pgtable_deposit arch_needs_pgtable_deposit
 static inline bool arch_needs_pgtable_deposit(void)
 {

@@ -1146,6 +1161,26 @@ static inline bool arch_needs_pgtable_deposit(void)
        return true;
 }

+static inline pmd_t pmd_mkdevmap(pmd_t pmd)
+{
+       return pte_pmd(pte_mkdevmap(pmd_pte(pmd)));
+}
+
+static inline int pmd_devmap(pmd_t pmd)
+{
+       return pte_devmap(pmd_pte(pmd));
+}

This should be defined only if #ifdef __HAVE_ARCH_PTE_DEVMAP

ok

The rest looks OK

Balbir Singh.