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Re: [PATCH for-5.0] vl.c: fix migration failure for 3.1 and older machin
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH for-5.0] vl.c: fix migration failure for 3.1 and older machine types |
Date: |
Tue, 24 Mar 2020 18:59:56 +0000 |
User-agent: |
Mutt/1.13.3 (2020-01-12) |
* Igor Mammedov (address@hidden) wrote:
> On Wed, 4 Mar 2020 12:27:48 -0500
> Igor Mammedov <address@hidden> wrote:
>
> > 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 <address@hidden>
> > Reported-by: Lukáš Doktor <address@hidden>
>
>
> ping,
>
> so we don't forget to merge it
I'm queueing this.
> > ---
> > CC: address@hidden
> > CC: address@hidden
> > CC: address@hidden
> > ---
> > softmmu/vl.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/softmmu/vl.c b/softmmu/vl.c
> > index 5549f4b619..1101b1cb41 100644
> > --- a/softmmu/vl.c
> > +++ b/softmmu/vl.c
> > @@ -2800,6 +2800,9 @@ 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",
>
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK