powerpc/64s/radix: prefetch user address in update_mmu_cache

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 <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index c3c39b0..8cecda4 100644 (file)
--- 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 82fed87..c1f4ca4 100644 (file)
--- 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 */