[PATCH v3 01/12] x86/mm: Avoid hard-coding PAT in get_page_from_l1e()

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

get_page_from_l1e() relied on Xen's choice of PAT, which is brittle in
the face of future PAT changes.  Use the proper _PAGE_* constants
instead.  Also, treat the two unused cases as if they are cacheable, as
future changes may make them cacheable.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/x86/mm.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 
78b1972e4170cacccc9c37c6e64e76e66a7da87f..b73cb29327ba49703673886d09d79f2f8928a6c0
 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -959,14 +959,19 @@ get_page_from_l1e(
             flip = _PAGE_RW;
         }
 
+        /* Force cacheable memtypes to UC */
         switch ( l1f & PAGE_CACHE_ATTRS )
         {
-        case 0: /* WB */
-            flip |= _PAGE_PWT | _PAGE_PCD;
+        case _PAGE_UC:
+        case _PAGE_UCM:
+        case _PAGE_WC:
+            /* not cached */
             break;
-        case _PAGE_PWT: /* WT */
-        case _PAGE_PWT | _PAGE_PAT: /* WP */
-            flip |= _PAGE_PCD | (l1f & _PAGE_PAT);
+        case _PAGE_WB:
+        case _PAGE_WT:
+        case _PAGE_WP:
+        default:
+            flip |= (l1f & PAGE_CACHE_ATTRS) ^ _PAGE_UC;
             break;
         }
 
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab