From 20a401a160bb959469e95cc809b53609eedccb40 Mon Sep 17 00:00:00 2001
From: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Date: Thu, 8 May 2014 11:27:33 +0200
Subject: [PATCH 08/31] Count used RAMBlock pages for migration_dirty_pages

RH-Author: Dr. David Alan Gilbert (git) <dgilbert@redhat.com>
Message-id: <1399548453-9181-2-git-send-email-dgilbert@redhat.com>
Patchwork-id: 58746
O-Subject: [RHEL7.1/RHEL7.0.z qemu-kvm PATCH 1/1] Count used RAMBlock pages for migration_dirty_pages
Bugzilla: 1074913
RH-Acked-by: Juan Quintela <quintela@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>
RH-Acked-by: Amit Shah <amit.shah@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

This is a fix for a bug* triggered by a migration after hot unplugging
a few virtio-net NICs, that caused migration never to converge, because
'migration_dirty_pages' is incorrectly initialised.

'migration_dirty_pages' is used as a tally of the number of outstanding
dirty pages, to give the migration code an idea of how much more data
will need to be transferred, and thus whether it can end the iterative
phase.

It was initialised to the total size of the RAMBlock address space,
however hotunplug can leave this space sparse, and hence
migration_dirty_pages ended up too large.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(* https://bugzilla.redhat.com/show_bug.cgi?id=1074913 )

Signed-off-by: Juan Quintela <quintela@redhat.com>
(cherry picked from commit e30d1d8c7195848abb28a8c734a82b845b8b456a)
---
 arch_init.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 arch_init.c |   21 +++++++++++++++++----
 1 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 22f7def..b88d686 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -728,11 +728,8 @@ static void reset_ram_globals(void)
 static int ram_save_setup(QEMUFile *f, void *opaque)
 {
     RAMBlock *block;
-    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+    int64_t ram_bitmap_pages; /* Size of bitmap in pages, including gaps */
 
-    migration_bitmap = bitmap_new(ram_pages);
-    bitmap_set(migration_bitmap, 0, ram_pages);
-    migration_dirty_pages = ram_pages;
     mig_throttle_on = false;
     dirty_rate_high_cnt = 0;
 
@@ -771,6 +768,22 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     bytes_transferred = 0;
     reset_ram_globals();
 
+    ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
+    migration_bitmap = bitmap_new(ram_bitmap_pages);
+    bitmap_set(migration_bitmap, 0, ram_bitmap_pages);
+
+    /*
+     * Count the total number of pages used by ram blocks not including any
+     * gaps due to alignment or unplugs.
+     */
+    migration_dirty_pages = 0;
+    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
+        uint64_t block_pages;
+
+        block_pages = block->length >> TARGET_PAGE_BITS;
+        migration_dirty_pages += block_pages;
+    }
+
     memory_global_dirty_log_start();
     migration_bitmap_sync();
     qemu_mutex_unlock_iothread();
-- 
1.7.1