Merge tag 'powerpc-4.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[cascardo/linux.git] / arch / powerpc / mm / hash_utils_64.c

diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 4e83d87..44d3c3a 100644 (file)
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -93,6 +93,9 @@ static unsigned long _SDR1;
 struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
 EXPORT_SYMBOL_GPL(mmu_psize_defs);
 
+u8 hpte_page_sizes[1 << LP_BITS];
+EXPORT_SYMBOL_GPL(hpte_page_sizes);
+
 struct hash_pte *htab_address;
 unsigned long htab_size_bytes;
 unsigned long htab_hash_mask;
@@ -564,8 +567,60 @@ static void __init htab_scan_page_sizes(void)
 #endif /* CONFIG_HUGETLB_PAGE */
 }
 
+/*
+ * Fill in the hpte_page_sizes[] array.
+ * We go through the mmu_psize_defs[] array looking for all the
+ * supported base/actual page size combinations.  Each combination
+ * has a unique pagesize encoding (penc) value in the low bits of
+ * the LP field of the HPTE.  For actual page sizes less than 1MB,
+ * some of the upper LP bits are used for RPN bits, meaning that
+ * we need to fill in several entries in hpte_page_sizes[].
+ *
+ * In diagrammatic form, with r = RPN bits and z = page size bits:
+ *        PTE LP     actual page size
+ *    rrrr rrrz                >=8KB
+ *    rrrr rrzz                >=16KB
+ *    rrrr rzzz                >=32KB
+ *    rrrr zzzz                >=64KB
+ *    ...
+ *
+ * The zzzz bits are implementation-specific but are chosen so that
+ * no encoding for a larger page size uses the same value in its
+ * low-order N bits as the encoding for the 2^(12+N) byte page size
+ * (if it exists).
+ */
+static void init_hpte_page_sizes(void)
+{
+       long int ap, bp;
+       long int shift, penc;
+
+       for (bp = 0; bp < MMU_PAGE_COUNT; ++bp) {
+               if (!mmu_psize_defs[bp].shift)
+                       continue;       /* not a supported page size */
+               for (ap = bp; ap < MMU_PAGE_COUNT; ++ap) {
+                       penc = mmu_psize_defs[bp].penc[ap];
+                       if (penc == -1)
+                               continue;
+                       shift = mmu_psize_defs[ap].shift - LP_SHIFT;
+                       if (shift <= 0)
+                               continue;       /* should never happen */
+                       /*
+                        * For page sizes less than 1MB, this loop
+                        * replicates the entry for all possible values
+                        * of the rrrr bits.
+                        */
+                       while (penc < (1 << LP_BITS)) {
+                               hpte_page_sizes[penc] = (ap << 4) | bp;
+                               penc += 1 << shift;
+                       }
+               }
+       }
+}
+
 static void __init htab_init_page_sizes(void)
 {
+       init_hpte_page_sizes();
+
        if (!debug_pagealloc_enabled()) {
                /*
                 * Pick a size for the linear mapping. Currently, we only