[PATCH 3.13 185/187] powerpc/mm: Use read barrier when creating real_pte

Kamal Mostafa
2014-09-15T23:01:11Z

From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>

commit 85c1fafd7262e68ad821ee1808686b1392b1167d upstream.

On ppc64 we support 4K hash pte with 64K page size. That requires
us to track the hash pte slot information on a per 4k basis. We do that
by storing the slot details in the second half of pte page. The pte bit
_PAGE_COMBO is used to indicate whether the second half need to be
looked while building real_pte. We need to use read memory barrier while
doing that so that load of hidx is not reordered w.r.t _PAGE_COMBO
check. On the store side we already do a lwsync in __hash_page_4K

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
arch/powerpc/include/asm/pte-hash64-64k.h | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/pte-hash64-64k.h b/arch/powerpc/include/asm/pte-hash64-64k.h
index d836d94..9ecede1 100644
--- a/arch/powerpc/include/asm/pte-hash64-64k.h
+++ b/arch/powerpc/include/asm/pte-hash64-64k.h
@@ -46,11 +46,31 @@
* in order to deal with 64K made of 4K HW pages. Thus we override the
* generic accessors and iterators here
*/
-#define __real_pte(e,p) ((real_pte_t) { \
- (e), (pte_val(e) & _PAGE_COMBO) ? \
- (pte_val(*((p) + PTRS_PER_PTE))) : 0 })
-#define __rpte_to_hidx(r,index) ((pte_val((r).pte) & _PAGE_COMBO) ? \
- (((r).hidx >> ((index)<<2)) & 0xf) : ((pte_val((r).pte) >> 12) & 0xf))
+#define __real_pte __real_pte
+static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep)
+{
+ real_pte_t rpte;
+
+ rpte.pte = pte;
+ rpte.hidx = 0;
+ if (pte_val(pte) & _PAGE_COMBO) {
+ /*
+ * Make sure we order the hidx load against the _PAGE_COMBO
+ * check. The store side ordering is done in __hash_page_4K
+ */
+ smp_rmb();
+ rpte.hidx = pte_val(*((ptep) + PTRS_PER_PTE));
+ }
+ return rpte;
+}
+
+static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
+{
+ if ((pte_val(rpte.pte) & _PAGE_COMBO))
+ return (rpte.hidx >> (index<<2)) & 0xf;
+ return (pte_val(rpte.pte) >> 12) & 0xf;
+}
+
#define __rpte_to_pte(r) ((r).pte)
#define __rpte_sub_valid(rpte, index) \
(pte_val(rpte.pte) & (_PAGE_HPTE_SUB0 >> (index)))
--
1.9.1