[PATCH 2/5] xen: Introduce xen_modified_memory.

[Alex Bligh <alex@alex.org.uk>]

This function is to be used during live migration. Every write access to the
guest memory should call this funcion so the Xen tools knows which pages are
dirty.

Backport of 910b38e4dc4c37683c8b821e75a7f4cf095e4b21

Signed-off-by: Alex Bligh <alex@alex.org.uk>
---
 hw/xen.h   |    1 +
 xen-all.c  |   21 +++++++++++++++++++++
 xen-stub.c |    4 ++++
 3 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/hw/xen.h b/hw/xen.h
index 2162111..359a275 100644
--- a/hw/xen.h
+++ b/hw/xen.h
@@ -45,6 +45,7 @@ void xenstore_store_pv_console_info(int i, struct CharDriverState *chr);
 
 #if defined(NEED_CPU_H) && !defined(CONFIG_USER_ONLY)
 void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size);
+void xen_modified_memory(ram_addr_t start, ram_addr_t length);
 #endif
 
 #if defined(CONFIG_XEN) && CONFIG_XEN_CTRL_INTERFACE_VERSION < 400
diff --git a/xen-all.c b/xen-all.c
index 6b4e511..121289d 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -1135,3 +1135,24 @@ void destroy_hvm_domain(bool reboot)
         xc_interface_close(xc_handle);
     }
 }
+
+void xen_modified_memory(ram_addr_t start, ram_addr_t length)
+{
+    if (unlikely(cpu_physical_memory_get_dirty_tracking())) {
+        int rc;
+        ram_addr_t start_pfn, nb_pages;
+
+        if (length == 0) {
+            length = TARGET_PAGE_SIZE;
+        }
+        start_pfn = start >> TARGET_PAGE_BITS;
+        nb_pages = ((start + length + TARGET_PAGE_SIZE - 1) >> TARGET_PAGE_BITS)
+            - start_pfn;
+        rc = xc_hvm_modified_memory(xen_xc, xen_domid, start_pfn, nb_pages);
+        if (rc) {
+            fprintf(stderr,
+                    "%s failed for "RAM_ADDR_FMT" ("RAM_ADDR_FMT"): %i, %s\n",
+                    __func__, start, nb_pages, rc, strerror(-rc));
+        }
+    }
+}
diff --git a/xen-stub.c b/xen-stub.c
index 25317ec..7b54477 100644
--- a/xen-stub.c
+++ b/xen-stub.c
@@ -48,3 +48,7 @@ int xen_init(void)
 void qmp_xen_set_global_dirty_log(bool enable, Error **errp)
 {
 }
+
+void xen_modified_memory(ram_addr_t start, ram_addr_t length)
+{
+}
-- 
1.7.4.1