[Devel] [PATCH rh7 v2] x86/mm: Use dirty bit for non-linear files ptes

[Andrey Ryabinin]

Backported patchset "Workaround for Xeon Phi PTE A/D bits erratum"
caused - kernel BUG at mm/rmap.c:1305!

_PAGE_BIT_FILE is not present in upstream but still present
in RHEL7 kernel, so they did this:
   /* Pick a bit unaffected by the "KNL4 erratum": */
   #define _PAGE_BIT_FILE		_PAGE_BIT_PSE

   Which conflicts with ours code:
   #define _PAGE_SWP_SOFT_DIRTY	_PAGE_PSE

So, as temporary fix restore old value for _PAGE_FILE.
If we care about supporting Xeon Phi we could backport
remap_file_pages() emulation from upstream which removes uses _PAGE_FILE.

https://jira.sw.ru/browse/PSBM-52992

Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
Changes since v1 - fixed typo
 s/_PAGE_PIT_DIRTY/_PAGE_BIT_DIRTY

 arch/x86/include/asm/pgtable_types.h | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 6e43ed0..5a6a5be 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -29,12 +29,8 @@
 /* - if the user mapped it with PROT_NONE; pte_present gives true */
 #define _PAGE_BIT_PROTNONE	_PAGE_BIT_GLOBAL
 /* - set: nonlinear file mapping, saved PTE; unset:swap */
-#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
-/* Pick a bit unaffected by the "KNL4 erratum": */
-#define _PAGE_BIT_FILE		_PAGE_BIT_PSE
-#else
+/* TODO: FIX: The following bit is affected by the "KNL4 erratum": */
 #define _PAGE_BIT_FILE		_PAGE_BIT_DIRTY
-#endif
 
 #define _PAGE_PRESENT	(_AT(pteval_t, 1) << _PAGE_BIT_PRESENT)
 #define _PAGE_RW	(_AT(pteval_t, 1) << _PAGE_BIT_RW)
-- 
2.7.3