This patch enable the speculative page fault on the PowerPC
architecture.
This will try a speculative page fault without holding the mmap_sem,
if it returns with VM_FAULT_RETRY, the mmap_sem is acquired and the
traditional page fault processing is done.
Build on if CONFIG_SPF is defined (currently for BOOK3S_64 && SMP).
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/mm/fault.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4797d08581ce..c018c2554cc8 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -442,6 +442,20 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
if (is_exec)
flags |= FAULT_FLAG_INSTRUCTION;
+#ifdef CONFIG_SPF
+ if (is_user) {
+ /* let's try a speculative page fault without grabbing the
+ * mmap_sem.
+ */
+ fault = handle_speculative_fault(mm, address, flags);
+ if (!(fault & VM_FAULT_RETRY)) {
+ perf_sw_event(PERF_COUNT_SW_SPF, 1,
+ regs, address);
+ goto done;
+ }
+ }
+#endif /* CONFIG_SPF */
+
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
@@ -526,6 +540,9 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
up_read(¤t->mm->mmap_sem);
+#ifdef CONFIG_SPF
+done:
+#endif
if (unlikely(fault & VM_FAULT_ERROR))
return mm_fault_error(regs, address, fault);
--
2.7.4
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