[RFC PATCH v2 12/21] fix live-migration when "populated=on" is missing

[Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>]

Live migration works after memory hot-add events, as long as the
qemu command line "-dimm" arguments are changed on the destination host
to specify "populated=on" for the dimms that have been hot-added.

If a command-line change has not occured, the destination host does not yet
have the corresponding ramblock in its ram_list. Activate the memslot on the
destination during ram_load.

Perhaps several fields of the DimmState struct should be part of a
VMStateDescription to handle migration in a cleaner way.

Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>
---
 arch_init.c |   23 ++++++++++++++++++++---
 1 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index a9e8b74..5f46b98 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -43,6 +43,7 @@
 #include "hw/smbios.h"
 #include "exec-memory.h"
 #include "hw/pcspk.h"
+#include "hw/dimm.h"
 
 #ifdef TARGET_SPARC
 int graphic_width = 1024;
@@ -452,9 +453,25 @@ int ram_load(QEMUFile *f, void *opaque, int version_id)
                     }
 
                     if (!block) {
-                        fprintf(stderr, "Unknown ramblock \"%s\", cannot "
-                                "accept migration\n", id);
-                        return -EINVAL;
+                        /* this can happen if a dimm was hot-added at source host */
+                        DimmState *slot = dimm_find_from_name(id);
+                        if (slot) {
+                            dimm_activate(slot);
+                            /* rescan ram_list, verify ramblock is there now */
+                            QLIST_FOREACH(block, &ram_list.blocks, next) {
+                                if (!strncmp(id, block->idstr, sizeof(id))) {
+                                    if (block->length != length)
+                                        return -EINVAL;
+                                    break;
+                                }
+                            }
+                            assert(block);
+                        }
+                        else {
+                            fprintf(stderr, "Unknown ramblock \"%s\", cannot "
+                                    "accept migration\n", id);
+                            return -EINVAL;
+                        }
                     }
 
                     total_ram_bytes -= length;
-- 
1.7.9