[Qemu-devel] [PATCH v1 13/17] background snapshot: add write-protected page access handler function

[Denis Plotnikov]

The handler does all the necessary operations to save the page being
accessed to the snapshot file(stream).

Signed-off-by: Denis Plotnikov <address@hidden>
---
 migration/ram.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 migration/ram.h |  1 +
 2 files changed, 44 insertions(+)

diff --git a/migration/ram.c b/migration/ram.c
index b1623e96e7..04a4bf708d 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1762,6 +1762,49 @@ int ram_copy_page(RAMBlock *block, unsigned long page_nr,
     return 1;
 }
 
+/**
+ * ram_process_page_fault
+ *
+ * Used in the background snapshot to queue the copy of the memory
+ * page for writing.
+ *
+ * Returns:
+ *    0 > - on error
+ *    0   - success
+ *
+ * @address:  guest address
+ *
+ */
+int ram_process_page_fault(void *address)
+{
+    int ret;
+    void *page_copy = NULL;
+    unsigned long page_nr;
+    ram_addr_t offset;
+
+    RAMBlock *block = ram_bgs_block_find(address, &offset);
+
+    if (!block) {
+        return -1;
+    }
+
+    page_nr = offset >> TARGET_PAGE_BITS;
+
+    ret = ram_copy_page(block, page_nr, &page_copy);
+
+    if (ret < 0) {
+        return ret;
+    } else if (ret > 0) {
+        if (ram_save_queue_pages(block, NULL, offset,
+                                 TARGET_PAGE_SIZE, page_copy)) {
+            ram_page_buffer_free(page_copy);
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
 /**
  * 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 76ab0a3377..2b565ce620 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -76,4 +76,5 @@ int ram_block_list_set_readonly(void);
 int ram_block_list_set_writable(void);
 
 int ram_copy_page(RAMBlock *block, unsigned long page_nr, void **page_copy);
+int ram_process_page_fault(void *address);
 #endif
-- 
2.17.0