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 WM_FAULT_RETRY, the mmap_sem is acquired and the
traditional page fault processing is done.
Support is only provide for BOOK3S_64 currently because:
- require CONFIG_PPC_STD_MMU because checks done in
set_access_flags_filter()
- require BOOK3S because we can't support for book3e_hugetlb_preload()
called by update_mmu_cache()
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/book3s/64/pgtable.h | 5 +++++
arch/powerpc/mm/fault.c | 30 +++++++++++++++++++++++++++-
2 files changed, 34 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 818a58fc3f4f..897f8b9f67e6 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -313,6 +313,11 @@ extern unsigned long pci_io_base;
/* Advertise support for _PAGE_SPECIAL */
#define __HAVE_ARCH_PTE_SPECIAL
+/* Advertise that we call the Speculative Page Fault handler */
+#if defined(CONFIG_PPC_BOOK3S_64)
+#define __HAVE_ARCH_CALL_SPF
+#endif
+
#ifndef __ASSEMBLY__
/*
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 4c422632047b..7b3cc4c30eab 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -291,9 +291,36 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
if (is_write && is_user)
store_update_sp = store_updates_sp(regs);
- if (is_user)
+ if (is_user) {
flags |= FAULT_FLAG_USER;
+#if defined(__HAVE_ARCH_CALL_SPF)
+ /* let's try a speculative page fault without grabbing the
+ * mmap_sem.
+ */
+
+ /*
+ * flags is set later based on the VMA's flags, for the common
+ * speculative service, we need some flags to be set.
+ */
+ if (is_write)
+ flags |= FAULT_FLAG_WRITE;
+
+ fault = handle_speculative_fault(mm, address, flags);
+ if (!(fault & VM_FAULT_RETRY || fault & VM_FAULT_ERROR)) {
+ perf_sw_event(PERF_COUNT_SW_SPF_DONE, 1,
+ regs, address);
+ goto done;
+ }
+
+ /*
+ * Resetting flags since the following code assumes
+ * FAULT_FLAG_WRITE is not set.
+ */
+ flags &= ~FAULT_FLAG_WRITE;
+#endif /* defined(__HAVE_ARCH_CALL_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
@@ -479,6 +506,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
rc = 0;
}
+done:
/*
* Major/minor page fault accounting.
*/
--
2.7.4
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