[Qemu-devel] [PATCH 1/4] migration: add RAMBlock's offset validation

[Yury Kotov <yury-kotov@yandex-team.ru>]

RAM migration has a RAMBlock validation stage (flag RAM_SAVE_FLAG_MEM_SIZE).
In this stage QEMU checks further information about RAMBlock:
1. Presence (by idstr),
2. Length (trying to resize, when differs),
3. Optional page size.

This patch adds a check for RAMBlock's offset. Currently we check it during
RAM pages loading - every RAM page has an offset in its header. But there is a
case when we don't send RAM pages (see below).

The following commits introduce a capability (ignore-external) to skip some
RAM blocks from migration. In such case the migration stream contains only
meta information about RAM blocks to validate them. So, the only way to check
block's offset is to send it explicitly.

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
---
 migration/ram.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index 7e7deec4d8..39629254e1 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3171,6 +3171,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
         if (migrate_postcopy_ram() && block->page_size != qemu_host_page_size) {
             qemu_put_be64(f, block->page_size);
         }
+        qemu_put_be64(f, block->offset);
     }
 
     rcu_read_unlock();
@@ -4031,7 +4032,7 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
 
     seq_iter++;
 
-    if (version_id != 4) {
+    if (version_id < 4) {
         ret = -EINVAL;
     }
 
@@ -4132,6 +4133,16 @@ static int ram_load(QEMUFile *f, void *opaque, int version_id)
                             ret = -EINVAL;
                         }
                     }
+                    if (version_id >= 5) {
+                        ram_addr_t offset;
+                        offset = qemu_get_be64(f);
+                        if (block->offset != offset) {
+                            error_report("Mismatched RAM block offset %s "
+                                         "%" PRId64 "!= %" PRId64,
+                                         id, offset, (uint64_t)block->offset);
+                            ret = -EINVAL;
+                        }
+                    }
                     ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
                                           block->idstr);
                 } else {
@@ -4363,5 +4374,5 @@ static SaveVMHandlers savevm_ram_handlers = {
 void ram_mig_init(void)
 {
     qemu_mutex_init(&XBZRLE.lock);
-    register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, &ram_state);
+    register_savevm_live(NULL, "ram", 0, 5, &savevm_ram_handlers, &ram_state);
 }
-- 
2.20.1