[PATCH] ARC: fix compile time assert fail for the config with PAE40 and 4K pages

[Pavel.Kozlov at synopsys.com]

From: Pavel Kozlov <pavel.kozlov at synopsys.com>

Add support for the configuration with 4K Page Size and enabled ARC_PAE40.
Set two-level Page Table to 10:9:12, as with PAE40 a 4k page can settle
only 512 entries (with PAE40 size of PTE entry increases from 4 to 8
bytes).

In this configuration the Page Table can describe only 31-bit (2Gb) virtual
space, but it is not a problem as the ARC MMUv4 supports only 2Gb of
virtual address.
This patch doesn't affect other configurations.

Patch fixes compile time assert fail:

  include/linux/compiler_types.h:328:45: error:
  call to '__compiletime_assert_288' declared with attribute error:
  BUILD_BUG_ON failed: (PTRS_PER_PTE * sizeof(pte_t)) > PAGE_SIZE

Reported-by: kernel test robot <lkp at intel.com>
Signed-off-by: Pavel Kozlov <pavel.kozlov at synopsys.com>
---
Added the same ARC_VADDR_BITS macro name as used in ARCv3 port.
The 4K Page Size and enabled PAE configuration was tested on nSIM:
load, allocation/free of all memory (low and high), user space
tests from glibc test suite (malloc, string).

 arch/arc/include/asm/pgtable-levels.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/arch/arc/include/asm/pgtable-levels.h b/arch/arc/include/asm/pgtable-levels.h
index ef68758b69f7..3b6afee9c272 100644
--- a/arch/arc/include/asm/pgtable-levels.h
+++ b/arch/arc/include/asm/pgtable-levels.h
@@ -42,12 +42,22 @@
  * (so 4K page can only have 1K entries: or 10 bits)
  */
 #ifdef CONFIG_ARC_PAGE_SIZE_4K
+#ifdef CONFIG_ARC_HAS_PAE40
+/*
+ * For PAE40 and 4K page size set 10:9:12 Page Table
+ * (as with PAE40 4k page can only have 512 entries)
+ * Page Table can describe only 31-bit (2Gb) virtual space
+ */
+#define PGDIR_SHIFT		21
+#define ARC_VADDR_BITS		31
+#else
 #define PGDIR_SHIFT		22
+#endif /* CONFIG_ARC_HAS_PAE40 */
 #else
 #define PGDIR_SHIFT		21
-#endif
+#endif /* CONFIG_ARC_PAGE_SIZE_4K */
 
-#endif
+#endif /* CONFIG_ARC_HUGEPAGE_16M */
 
 #else /* CONFIG_PGTABLE_LEVELS != 2 */
 
@@ -67,9 +77,13 @@
 
 #endif /* CONFIG_PGTABLE_LEVELS */
 
+#ifndef ARC_VADDR_BITS
+#define ARC_VADDR_BITS	32
+#endif
+
 #define PGDIR_SIZE		BIT(PGDIR_SHIFT)
 #define PGDIR_MASK		(~(PGDIR_SIZE - 1))
-#define PTRS_PER_PGD		BIT(32 - PGDIR_SHIFT)
+#define PTRS_PER_PGD		BIT(ARC_VADDR_BITS - PGDIR_SHIFT)
 
 #if CONFIG_PGTABLE_LEVELS > 3
 #define PUD_SIZE		BIT(PUD_SHIFT)
-- 
2.25.1