powerpc: Free a PTE bit on ppc64 with 64K pages
This frees a PTE bit when using 64K pages on ppc64. This is done
by getting rid of the separate _PAGE_HASHPTE bit. Instead, we just test
if any of the 16 sub-page bits is set. For non-combo pages (ie. real
64K pages), we set SUB0 and the location encoding in that field.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/pgtable-64k.h b/include/asm-powerpc/pgtable-64k.h
index 1cbd6b3..c500771 100644
--- a/include/asm-powerpc/pgtable-64k.h
+++ b/include/asm-powerpc/pgtable-64k.h
@@ -75,6 +75,20 @@
#define _PAGE_COMBO 0x10000000 /* this is a combo 4k page */
#define _PAGE_4K_PFN 0x20000000 /* PFN is for a single 4k page */
+/* For 64K page, we don't have a separate _PAGE_HASHPTE bit. Instead,
+ * we set that to be the whole sub-bits mask. The C code will only
+ * test this, so a multi-bit mask will work. For combo pages, this
+ * is equivalent as effectively, the old _PAGE_HASHPTE was an OR of
+ * all the sub bits. For real 64k pages, we now have the assembly set
+ * _PAGE_HPTE_SUB0 in addition to setting the HIDX bits which overlap
+ * that mask. This is fine as long as the HIDX bits are never set on
+ * a PTE that isn't hashed, which is the case today.
+ *
+ * A little nit is for the huge page C code, which does the hashing
+ * in C, we need to provide which bit to use.
+ */
+#define _PAGE_HASHPTE _PAGE_HPTE_SUB
+
/* Note the full page bits must be in the same location as for normal
* 4k pages as the same asssembly will be used to insert 64K pages
* wether the kernel has CONFIG_PPC_64K_PAGES or not
@@ -83,8 +97,7 @@
#define _PAGE_F_GIX 0x00007000 /* full page: hidx bits */
/* PTE flags to conserve for HPTE identification */
-#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | _PAGE_HPTE_SUB |\
- _PAGE_COMBO)
+#define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | _PAGE_COMBO)
/* Shift to put page number into pte.
*