accel/tcg: Make page_alloc_target_data allocation constant

Use a constant target data allocation size for all pages.
This will be necessary to reduce overhead of page tracking.
Since TARGET_PAGE_DATA_SIZE is now required, we can use this
to omit data tracking for targets that don't require it.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/translate-all.c

@@ -2271,6 +2271,7 @@ void page_set_flags(target_ulong start, target_ulong end, int flags)
 
 void page_reset_target_data(target_ulong start, target_ulong end)
 {
+#ifdef TARGET_PAGE_DATA_SIZE
     target_ulong addr, len;
 
     /*
@@ -2293,27 +2294,30 @@ void page_reset_target_data(target_ulong start, target_ulong end)
         g_free(p->target_data);
         p->target_data = NULL;
     }
+#endif
 }
 
+#ifdef TARGET_PAGE_DATA_SIZE
 void *page_get_target_data(target_ulong address)
 {
     PageDesc *p = page_find(address >> TARGET_PAGE_BITS);
     return p ? p->target_data : NULL;
 }
 
-void *page_alloc_target_data(target_ulong address, size_t size)
+void *page_alloc_target_data(target_ulong address)
 {
     PageDesc *p = page_find(address >> TARGET_PAGE_BITS);
     void *ret = NULL;
 
     if (p->flags & PAGE_VALID) {
         ret = p->target_data;
         if (!ret) {
-            p->target_data = ret = g_malloc0(size);
+            p->target_data = ret = g_malloc0(TARGET_PAGE_DATA_SIZE);
         }
     }
     return ret;
 }
+#endif /* TARGET_PAGE_DATA_SIZE */
 
 int page_check_range(target_ulong start, target_ulong len, int flags)
 {

include/exec/cpu-all.h

@@ -281,19 +281,18 @@ void page_reset_target_data(target_ulong start, target_ulong end);
 int page_check_range(target_ulong start, target_ulong len, int flags);
 
 /**
- * page_alloc_target_data(address, size)
+ * page_alloc_target_data(address)
  * @address: guest virtual address
- * @size: size of data to allocate
  *
- * Allocate @size bytes of out-of-band data to associate with the
- * guest page at @address.  If the page is not mapped, NULL will
+ * Allocate TARGET_PAGE_DATA_SIZE bytes of out-of-band data to associate
+ * with the guest page at @address.  If the page is not mapped, NULL will
  * be returned.  If there is existing data associated with @address,
  * no new memory will be allocated.
  *
  * The memory will be freed when the guest page is deallocated,
  * e.g. with the munmap system call.
  */
-void *page_alloc_target_data(target_ulong address, size_t size);
+void *page_alloc_target_data(target_ulong address);
 
 /**
  * page_get_target_data(address)

target/arm/cpu.h

@@ -3410,6 +3410,14 @@ extern const uint64_t pred_esz_masks[5];
 #define PAGE_MTE            PAGE_TARGET_2
 #define PAGE_TARGET_STICKY  PAGE_MTE
 
+/* We associate one allocation tag per 16 bytes, the minimum.  */
+#define LOG2_TAG_GRANULE 4
+#define TAG_GRANULE      (1 << LOG2_TAG_GRANULE)
+
+#ifdef CONFIG_USER_ONLY
+#define TARGET_PAGE_DATA_SIZE (TARGET_PAGE_SIZE >> (LOG2_TAG_GRANULE + 1))
+#endif
+
 #ifdef TARGET_TAGGED_ADDRESSES
 /**
  * cpu_untagged_addr:

target/arm/internals.h

@@ -1164,10 +1164,6 @@ void arm_log_exception(CPUState *cs);
  */
 #define GMID_EL1_BS  6
 
-/* We associate one allocation tag per 16 bytes, the minimum.  */
-#define LOG2_TAG_GRANULE 4
-#define TAG_GRANULE      (1 << LOG2_TAG_GRANULE)
-
 /*
  * SVE predicates are 1/8 the size of SVE vectors, and cannot use
  * the same simd_desc() encoding due to restrictions on size.

target/arm/mte_helper.c

@@ -96,8 +96,7 @@ static uint8_t *allocation_tag_mem(CPUARMState *env, int ptr_mmu_idx,
 
     tags = page_get_target_data(clean_ptr);
     if (tags == NULL) {
-        size_t alloc_size = TARGET_PAGE_SIZE >> (LOG2_TAG_GRANULE + 1);
-        tags = page_alloc_target_data(clean_ptr, alloc_size);
+        tags = page_alloc_target_data(clean_ptr);
         assert(tags != NULL);
     }