[Qemu-devel] [PATCH 01/19] Add support for multi-level phys map.

[Tristan Gingold <gingold@adacore.com>]

As Alpha physical addresses are 44 bits, l1_phys_map can't be anymore 2 levels.
Use a more generic multi-level approach and explain why we don't need to
extend l1_map.

Signed-off-by: Tristan Gingold <gingold@adacore.com>
---
 exec.c |   50 ++++++++++++++++++++++++++------------------------
 1 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/exec.c b/exec.c
index df22c79..4b2ebc2 100644
--- a/exec.c
+++ b/exec.c
@@ -147,15 +147,14 @@ typedef struct PhysPageDesc {
 } PhysPageDesc;
 
 #define L2_BITS 10
-#if defined(CONFIG_USER_ONLY) && defined(TARGET_VIRT_ADDR_SPACE_BITS)
-/* XXX: this is a temporary hack for alpha target.
- *      In the future, this is to be replaced by a multi-level table
- *      to actually be able to handle the complete 64 bits address space.
- */
-#define L1_BITS (TARGET_VIRT_ADDR_SPACE_BITS - L2_BITS - TARGET_PAGE_BITS)
+
+#define L1_BITS_ ((TARGET_PHYS_ADDR_SPACE_BITS - TARGET_PAGE_BITS) % L2_BITS)
+#if L1_BITS_ < 4 /* avoid ridiculous small l1 */
+#define L1_BITS (L1_BITS_ + L2_BITS)
 #else
-#define L1_BITS (32 - L2_BITS - TARGET_PAGE_BITS)
+#define L1_BITS L1_BITS_
 #endif
+#define L1_SHIFT (TARGET_PHYS_ADDR_SPACE_BITS - TARGET_PAGE_BITS - L1_BITS)
 
 #define L1_SIZE (1 << L1_BITS)
 #define L2_SIZE (1 << L2_BITS)
@@ -165,7 +164,9 @@ unsigned long qemu_host_page_bits;
 unsigned long qemu_host_page_size;
 unsigned long qemu_host_page_mask;
 
-/* XXX: for system emulation, it could just be an array */
+/* XXX: for system emulation, it could just be an array.  As this is currently
+   a two level map this limits the size of RAM memory that can contains
+   target code.  In practice this is large enough (>= 4GB) */
 static PageDesc *l1_map[L1_SIZE];
 static PhysPageDesc **l1_phys_map;
 
@@ -338,25 +339,26 @@ static PhysPageDesc *phys_page_find_alloc(target_phys_addr_t index, int alloc)
 {
     void **lp, **p;
     PhysPageDesc *pd;
+    int i;
 
+    /* Level 1.  */
     p = (void **)l1_phys_map;
-#if TARGET_PHYS_ADDR_SPACE_BITS > 32
+    lp = p + ((index >> L1_SHIFT) & (L1_SIZE - 1));
 
-#if TARGET_PHYS_ADDR_SPACE_BITS > (32 + L1_BITS)
-#error unsupported TARGET_PHYS_ADDR_SPACE_BITS
-#endif
-    lp = p + ((index >> (L1_BITS + L2_BITS)) & (L1_SIZE - 1));
-    p = *lp;
-    if (!p) {
-        /* allocate if not found */
-        if (!alloc)
-            return NULL;
-        p = qemu_vmalloc(sizeof(void *) * L1_SIZE);
-        memset(p, 0, sizeof(void *) * L1_SIZE);
-        *lp = p;
+    /* Level 2..n-1 */
+    for (i = (L1_SHIFT / L2_BITS) - 1; i > 0; i--) {
+        p = *lp;
+        if (!p) {
+            /* allocate if not found */
+            if (!alloc)
+                return NULL;
+            p = qemu_vmalloc(sizeof(void *) * L2_SIZE);
+            memset(p, 0, sizeof(void *) * L2_SIZE);
+            *lp = p;
+        }
+        lp = p + ((index >> (i * L2_BITS)) & (L2_SIZE - 1));
     }
-#endif
-    lp = p + ((index >> L2_BITS) & (L1_SIZE - 1));
+
     pd = *lp;
     if (!pd) {
         int i;
-- 
1.6.2