csky: mmu: Prevent spurious page faults

C-SKY MMU would pre-fetch invalid pte entries, and it could work with
flush_tlb_fix_spurious_fault, but the additional page fault exceptions
would reduce performance. So flushing the entry of the TLB would prevent
the following spurious page faults. Here is the test code:

define DATA_LEN  4096
define COPY_NUM  (504*100)

unsigned char src[DATA_LEN*COPY_NUM] = {0};
unsigned char dst[DATA_LEN*COPY_NUM] = {0};

unsigned char func_src[DATA_LEN*COPY_NUM] = {0};
unsigned char func_dst[DATA_LEN*COPY_NUM] = {0};

void main(void)
{
	int j;
	for (j = 0; j < COPY_NUM; j++)
		memcpy(&dst[j*DATA_LEN], &src[j*DATA_LEN], 4);
}

perf stat -e page-faults ./main.elf

The amount of page fault traps would be reduced in half with the patch.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/csky/abiv2/cacheflush.c b/arch/csky/abiv2/cacheflush.c
index 39c51399dd81..9923cd24db58 100644
--- a/arch/csky/abiv2/cacheflush.c
+++ b/arch/csky/abiv2/cacheflush.c
@@ -5,6 +5,7 @@
 #include <linux/highmem.h>
 #include <linux/mm.h>
 #include <asm/cache.h>
+#include <asm/tlbflush.h>
 
 void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 		      pte_t *pte)
@@ -12,6 +13,8 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 	unsigned long addr;
 	struct page *page;
 
+	flush_tlb_page(vma, address);
+
 	if (!pfn_valid(pte_pfn(*pte)))
 		return;