migration: Remove qemu_host_page_size

Replace with the maximum of the real host page size
and the target page size.  This is an exact replacement.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Acked-by: Helge Deller <deller@gmx.de>
Message-Id: <20240102015808.132373-12-richard.henderson@linaro.org>

migration/ram.c

@@ -2934,7 +2934,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
 {
     RAMState **rsp = opaque;
     RAMBlock *block;
-    int ret;
+    int ret, max_hg_page_size;
 
     if (compress_threads_save_setup()) {
         return -1;
@@ -2949,6 +2949,12 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     }
     (*rsp)->pss[RAM_CHANNEL_PRECOPY].pss_channel = f;
 
+    /*
+     * ??? Mirrors the previous value of qemu_host_page_size,
+     * but is this really what was intended for the migration?
+     */
+    max_hg_page_size = MAX(qemu_real_host_page_size(), TARGET_PAGE_SIZE);
+
     WITH_RCU_READ_LOCK_GUARD() {
         qemu_put_be64(f, ram_bytes_total_with_ignored()
                          | RAM_SAVE_FLAG_MEM_SIZE);
@@ -2957,8 +2963,8 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
             qemu_put_byte(f, strlen(block->idstr));
             qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
             qemu_put_be64(f, block->used_length);
-            if (migrate_postcopy_ram() && block->page_size !=
-                                          qemu_host_page_size) {
+            if (migrate_postcopy_ram() &&
+                block->page_size != max_hg_page_size) {
                 qemu_put_be64(f, block->page_size);
             }
             if (migrate_ignore_shared()) {
@@ -3791,6 +3797,7 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
     int ret = 0;
     /* ADVISE is earlier, it shows the source has the postcopy capability on */
     bool postcopy_advised = migration_incoming_postcopy_advised();
+    int max_hg_page_size;
 
     assert(block);
 
@@ -3808,9 +3815,16 @@ static int parse_ramblock(QEMUFile *f, RAMBlock *block, ram_addr_t length)
             return ret;
         }
     }
+
+    /*
+     * ??? Mirrors the previous value of qemu_host_page_size,
+     * but is this really what was intended for the migration?
+     */
+    max_hg_page_size = MAX(qemu_real_host_page_size(), TARGET_PAGE_SIZE);
+
     /* For postcopy we need to check hugepage sizes match */
     if (postcopy_advised && migrate_postcopy_ram() &&
-        block->page_size != qemu_host_page_size) {
+        block->page_size != max_hg_page_size) {
         uint64_t remote_page_size = qemu_get_be64(f);
         if (remote_page_size != block->page_size) {
             error_report("Mismatched RAM page size %s "