arm64: Reduce PT size estimation complexity

count_required_pts()'s complexity is high if mappings are not using the
largest possible block size (due to some other requirement such as tracking
dirty pages, for example).

Let's switch to a method that follows the pattern established with
the add_map() helper, and make it almost instantaneous instead of
taking a large amount of time if 2MB mappings are in use instead of
1GB.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
[ Paul: pick from the Android tree. Fixup Pierre's commit. Rebase to the
  upstream ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Tom Rini <trini@konsulko.com>
Link: https://android.googlesource.com/platform/external/u-boot/+/5d756d147e31a1cdaaa261a50e526404ca5968f5
Link: https://android.googlesource.com/platform/external/u-boot/+/6be9330601d81545c7c941e3609f35bf68a09059

diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
index 876344e..6973340 100644 (file)
--- a/arch/arm/cpu/armv8/cache_v8.c
+++ b/arch/arm/cpu/armv8/cache_v8.c
@@ -352,98 +352,57 @@ static void add_map(struct mm_region *map)
                  (u64 *)gd->arch.tlb_addr, attrs);
 }
 
-enum pte_type {
-       PTE_INVAL,
-       PTE_BLOCK,
-       PTE_LEVEL,
-};
-
-/*
- * This is a recursively called function to count the number of
- * page tables we need to cover a particular PTE range. If you
- * call this with level = -1 you basically get the full 48 bit
- * coverage.
- */
-static int count_required_pts(u64 addr, int level, u64 maxaddr)
+static void count_range(u64 virt, u64 size, int level, int *cntp)
 {
-       int levelshift = level2shift(level);
-       u64 levelsize = 1ULL << levelshift;
-       u64 levelmask = levelsize - 1;
-       u64 levelend = addr + levelsize;
-       int r = 0;
-       int i;
-       enum pte_type pte_type = PTE_INVAL;
+       u64 map_size = BIT_ULL(level2shift(level));
+       int i, idx;
 
-       for (i = 0; mem_map[i].size || mem_map[i].attrs; i++) {
-               struct mm_region *map = &mem_map[i];
-               u64 start = map->virt;
-               u64 end = start + map->size;
+       idx = (virt >> level2shift(level)) & (MAX_PTE_ENTRIES - 1);
+       for (i = idx; size; i++) {
+               u64 next_size;
 
-               /* Check if the PTE would overlap with the map */
-               if (max(addr, start) <= min(levelend, end)) {
-                       start = max(addr, start);
-                       end = min(levelend, end);
+               if (level >= 1 &&
+                   size >= map_size && !(virt & (map_size - 1))) {
+                       virt += map_size;
+                       size -= map_size;
 
-                       /* We need a sub-pt for this level */
-                       if ((start & levelmask) || (end & levelmask)) {
-                               pte_type = PTE_LEVEL;
-                               break;
-                       }
+                       continue;
+               }
 
-                       /* Lv0 can not do block PTEs, so do levels here too */
-                       if (level <= 0) {
-                               pte_type = PTE_LEVEL;
-                               break;
-                       }
+               /* Going one level down */
+               (*cntp)++;
+               next_size = min(map_size - (virt & (map_size - 1)), size);
 
-                       /* PTE is active, but fits into a block */
-                       pte_type = PTE_BLOCK;
-               }
-       }
+               count_range(virt, next_size, level + 1, cntp);
 
-       /*
-        * Block PTEs at this level are already covered by the parent page
-        * table, so we only need to count sub page tables.
-        */
-       if (pte_type == PTE_LEVEL) {
-               int sublevel = level + 1;
-               u64 sublevelsize = 1ULL << level2shift(sublevel);
-
-               /* Account for the new sub page table ... */
-               r = 1;
-
-               /* ... and for all child page tables that one might have */
-               for (i = 0; i < MAX_PTE_ENTRIES; i++) {
-                       r += count_required_pts(addr, sublevel, maxaddr);
-                       addr += sublevelsize;
-
-                       if (addr >= maxaddr) {
-                               /*
-                                * We reached the end of address space, no need
-                                * to look any further.
-                                */
-                               break;
-                       }
-               }
+               virt += next_size;
+               size -= next_size;
        }
-
-       return r;
 }
 
-/* Returns the estimated required size of all page tables */
-__weak u64 get_page_table_size(void)
+static int count_ranges(void)
 {
-       u64 one_pt = MAX_PTE_ENTRIES * sizeof(u64);
-       u64 size = 0;
+       int i, count = 0, level = 0;
        u64 va_bits;
-       int start_level = 0;
 
        get_tcr(NULL, &va_bits);
        if (va_bits < 39)
-               start_level = 1;
+               level = 1;
+
+       for (i = 0; mem_map[i].size || mem_map[i].attrs; i++)
+               count_range(mem_map[i].virt, mem_map[i].size, level, &count);
+
+       return count;
+}
+
+/* Returns the estimated required size of all page tables */
+__weak u64 get_page_table_size(void)
+{
+       u64 one_pt = MAX_PTE_ENTRIES * sizeof(u64);
+       u64 size;
 
        /* Account for all page tables we would need to cover our memory map */
-       size = one_pt * count_required_pts(0, start_level - 1, 1ULL << va_bits);
+       size = one_pt * count_ranges();
 
        /*
         * We need to duplicate our page table once to have an emergency pt to