[Qemu-devel] [PATCH] migrate: error message for ram_load size

[Doug Goldstein]

Report an error when ramblock's sizes mismatch with a suggestion to the
user as to what went wrong. If a user has a managedsave state by
libvirt, which is the default now, and upgrades their distro, which in
turn upgrades QEMU, they will be surprised by the fact that their VMs fail
to start. The reason for this is that the default ROM sizes changed
recently which makes it not possible to migrate from that saved state.
However the error message really does not provide details as to what
went wrong. This patch attempts to provide more details

see:
http://lists.nongnu.org/archive/html/qemu-devel/2012-10/msg03746.html
http://lists.nongnu.org/archive/html/qemu-devel/2012-10/msg04108.html
---
 arch_init.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 8c3bb0d..33f783b 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -810,6 +810,11 @@ static int ram_load(QEMUFile *f, void *opaque, int 
version_id)
                     QLIST_FOREACH(block, &ram_list.blocks, next) {
                         if (!strncmp(id, block->idstr, sizeof(id))) {
                             if (block->length != length) {
+                                fprintf(stderr, "qemu: warning: error ramblock 
"
+                                        "'%s' length %ld != %ld. Did you "
+                                        "change the ROM/BIOS or RAM size "
+                                        "between restarts?\n", id,
+                                        block->length, length);
                                 ret =  -EINVAL;
                                 goto done;
                             }
-- 
1.7.8.6