From d96c4d5f193e0e45beec80a6277728b32875bddb Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Wed, 4 Mar 2020 12:27:48 -0500 Subject: [PATCH] vl.c: fix migration failure for 3.1 and older machine types MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Migration from QEMU(v4.0) fails when using 3.1 or older machine type. For example if one attempts to migrate QEMU-2.12 started as qemu-system-ppc64 -nodefaults -M pseries-2.12 -m 4096 -mem-path /tmp/ to current master, it will fail with qemu-system-ppc64: Unknown ramblock "ppc_spapr.ram", cannot accept migration qemu-system-ppc64: error while loading state for instance 0x0 of device 'ram' qemu-system-ppc64: load of migration failed: Invalid argument Caused by 900c0ba373 commit which switches main RAM allocation to memory backends and the fact in 3.1 and older QEMU, backends used full[***] QOM path as memory region name instead of backend's name. That was changed after 3.1 to use prefix-less names by default (fa0cb34d22) for new machine types. *** effectively makes main RAM memory region names defined by MachineClass::default_ram_id being altered with '/objects/' prefix and therefore migration fails as old QEMU sends prefix-less name while new QEMU expects name with prefix when using 3.1 and older machine types. Fix it by forcing implicit[1] memory backend to always use prefix-less names for its memory region by setting 'x-use-canonical-path-for-ramblock-id' property to false. 1) i.e. memory backend created by compat glue which maps -m/-mem-path/-mem-prealloc/default RAM size into appropriate backend type/options to match old CLI format. Fixes: 900c0ba373 Signed-off-by: Igor Mammedov Reported-by: Lukáš Doktor Message-Id: <20200304172748.15338-1-imammedo@redhat.com> Tested-by: Lukáš Doktor Reviewed-by: Marc-André Lureau Signed-off-by: Dr. David Alan Gilbert --- softmmu/vl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/softmmu/vl.c b/softmmu/vl.c index 1d33a28340..814537bb42 100644 --- a/softmmu/vl.c +++ b/softmmu/vl.c @@ -2801,6 +2801,9 @@ static void create_default_memdev(MachineState *ms, const char *path) object_property_set_int(obj, ms->ram_size, "size", &error_fatal); object_property_add_child(object_get_objects_root(), mc->default_ram_id, obj, &error_fatal); + /* Ensure backend's memory region name is equal to mc->default_ram_id */ + object_property_set_bool(obj, false, "x-use-canonical-path-for-ramblock-id", + &error_fatal); user_creatable_complete(USER_CREATABLE(obj), &error_fatal); object_unref(obj); object_property_set_str(OBJECT(ms), mc->default_ram_id, "memory-backend", -- 2.11.4.GIT