[PATCH v4 4/7] powerpc/64s/radix: prefetch user address in update_mmu_cache

[Nicholas Piggin]

Prefetch the faulting address in update_mmu_cache to give the page
table walker perhaps 100 cycles head start as locks are dropped and
the interrupt completed.

Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 arch/powerpc/mm/mem.c              | 4 +++-
 arch/powerpc/mm/pgtable-book3s64.c | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index c3c39b02b2ba..8cecda4bd66a 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -509,8 +509,10 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned 
long address,
         */
        unsigned long access, trap;
 
-       if (radix_enabled())
+       if (radix_enabled()) {
+               prefetch((void *)address);
                return;
+       }
 
        /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
        if (!pte_young(*ptep) || address >= TASK_SIZE)
diff --git a/arch/powerpc/mm/pgtable-book3s64.c 
b/arch/powerpc/mm/pgtable-book3s64.c
index 82fed87289de..c1f4ca45c93a 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/arch/powerpc/mm/pgtable-book3s64.c
@@ -152,7 +152,8 @@ pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
                          pmd_t *pmd)
 {
-       return;
+       if (radix_enabled())
+               prefetch((void *)addr);
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
-- 
2.17.0