[Qemu-devel] [PATCH v1 06/17] background snapshot: add helpers to manage a copy of ram block list

[Denis Plotnikov <dplotnikov@virtuozzo.com>]

The VM ramblock list may be changed during the snapshotting.
We want to make sure that we have the same ramblock list as it
was at the time of snapshot beginning.
So, we create a copy of the list at the beginning of the snapshotting
and use it during the process.

Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
 migration/ram.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++
 migration/ram.h |  6 ++++++
 2 files changed, 57 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index 021d583b9b..4399c31606 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1508,6 +1508,57 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
     return pages;
 }
 
+/* BackGround Snapshot Blocks */
+static RamBlockList bgs_blocks;
+
+static RamBlockList *ram_bgs_block_list_get(void)
+{
+    return &bgs_blocks;
+}
+
+void ram_block_list_create(void)
+{
+    RAMBlock *block = NULL;
+    RamBlockList *block_list = ram_bgs_block_list_get();
+
+    qemu_mutex_lock_ramlist();
+    QLIST_FOREACH(block, &ram_list.blocks, next) {
+        memory_region_ref(block->mr);
+        QLIST_INSERT_HEAD(block_list, block, bgs_next);
+    }
+    qemu_mutex_unlock_ramlist();
+}
+
+void ram_block_list_destroy(void)
+{
+    RAMBlock *next, *block;
+    RamBlockList *block_list = ram_bgs_block_list_get();
+
+    QLIST_FOREACH_SAFE(block, block_list, bgs_next, next) {
+        QLIST_REMOVE(block, bgs_next);
+        memory_region_unref(block->mr);
+    }
+}
+
+RAMBlock *ram_bgs_block_find(uint8_t *address, ram_addr_t *page_offset)
+{
+    RAMBlock *block = NULL;
+    RamBlockList *block_list = ram_bgs_block_list_get();
+
+    QLIST_FOREACH(block, block_list, bgs_next) {
+        /* This case append when the block is not mapped. */
+        if (block->host == NULL) {
+            continue;
+        }
+
+        if (address - block->host < block->max_length) {
+            *page_offset = (address - block->host) & TARGET_PAGE_MASK;
+            return block;
+        }
+    }
+
+    return NULL;
+}
 /**
  * ram_find_and_save_block: finds a dirty page and sends it to f
  *
diff --git a/migration/ram.h b/migration/ram.h
index 64d81e9f1d..385579cae9 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -31,6 +31,7 @@
 
 #include "qemu-common.h"
 #include "exec/cpu-common.h"
+#include "exec/ramlist.h"
 
 extern MigrationStats ram_counters;
 extern XBZRLECacheStats xbzrle_counters;
@@ -61,5 +62,10 @@ void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
 int ramblock_recv_bitmap_test(RAMBlock *rb, void *host_addr);
 void ramblock_recv_bitmap_set(RAMBlock *rb, void *host_addr);
 void ramblock_recv_bitmap_set_range(RAMBlock *rb, void *host_addr, size_t nr);
+/* For background snapshot */
+void ram_block_list_create(void);
+void ram_block_list_destroy(void);
+
+RAMBlock *ram_bgs_block_find(uint8_t *address, ram_addr_t *page_offset);
 
 #endif
-- 
2.17.0