[PATCH 3.4 16/45] xtensa: fix TLBTEMP_BASE_2 region handling in fast_second_level_miss

Zefan Li
2014-09-23T02:37:04Z

From: Max Filippov <jcmvbkbc@gmail.com>

3.4.104-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit 7128039fe2dd3d59da9e4ffa036f3aaa3ba87b9f upstream.

Current definition of TLBTEMP_BASE_2 is always 32K above the
TLBTEMP_BASE_1, whereas fast_second_level_miss handler for the TLBTEMP
region analyzes virtual address bit (PAGE_SHIFT + DCACHE_ALIAS_ORDER)
to determine TLBTEMP region where the fault happened. The size of the
TLBTEMP region is also checked incorrectly: not 64K, but twice data
cache way size (whicht may as well be less than the instruction cache
way size).

Fix TLBTEMP_BASE_2 to be TLBTEMP_BASE_1 + data cache way size.
Provide TLBTEMP_SIZE that is a greater of doubled data cache way size or
the instruction cache way size, and use it to determine if the second
level TLB miss occured in the TLBTEMP region.

Practical occurence of page faults in the TLBTEMP area is extremely
rare, this code can be tested by deletion of all w[di]tlb instructions
in the tlbtemp_mapping region.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
arch/xtensa/include/asm/pgtable.h | 7 ++++++-
arch/xtensa/kernel/entry.S | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/xtensa/include/asm/pgtable.h b/arch/xtensa/include/asm/pgtable.h
index b03c043..7eeaf22 100644
--- a/arch/xtensa/include/asm/pgtable.h
+++ b/arch/xtensa/include/asm/pgtable.h
@@ -68,7 +68,12 @@
#define VMALLOC_START 0xC0000000
#define VMALLOC_END 0xC7FEFFFF
#define TLBTEMP_BASE_1 0xC7FF0000
-#define TLBTEMP_BASE_2 0xC7FF8000
+#define TLBTEMP_BASE_2 (TLBTEMP_BASE_1 + DCACHE_WAY_SIZE)
+#if 2 * DCACHE_WAY_SIZE > ICACHE_WAY_SIZE
+#define TLBTEMP_SIZE (2 * DCACHE_WAY_SIZE)
+#else
+#define TLBTEMP_SIZE ICACHE_WAY_SIZE
+#endif

/*
* Xtensa Linux config PTE layout (when present):
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 6223f33..bc9f78e 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1629,7 +1629,7 @@ ENTRY(fast_second_level_miss)
rsr a0, EXCVADDR
bltu a0, a3, 2f

- addi a1, a0, -(2 << (DCACHE_ALIAS_ORDER + PAGE_SHIFT))
+ addi a1, a0, -TLBTEMP_SIZE
bgeu a1, a3, 2f

/* Check if we have to restore an ITLB mapping. */
--
1.7.9.5