RE: [PATCH v3] migration: Don't allow migration if vm is in POSTMIGRATE

[Tuguoyi <tu.guoyi@h3c.com>]

Ping. 
It seems no one handle this patch. 


> -----Original Message-----
> From: Pankaj Gupta [mailto:pankaj.gupta.linux@gmail.com]
> Sent: Wednesday, December 09, 2020 10:21 PM
> To: tuguoyi (Cloud) <tu.guoyi@h3c.com>
> Cc: Juan Quintela <quintela@redhat.com>; Dr. David Alan Gilbert
> <dgilbert@redhat.com>; vsementsov@virtuozzo.com;
> qemu-devel@nongnu.org; Li Zhang <li.zhang@cloud.ionos.com>
> Subject: Re: [PATCH v3] migration: Don't allow migration if vm is in
> POSTMIGRATE
> 
> > The following steps will cause qemu assertion failure:
> > - pause vm by executing 'virsh suspend'
> > - create external snapshot of memory and disk using 'virsh
> snapshot-create-as'
> > - doing the above operation again will cause qemu crash
> >
> > The backtrace looks like:
> > #0  0x00007fbf958c5c37 in raise () from /lib/x86_64-linux-gnu/libc.so.6
> > #1  0x00007fbf958c9028 in abort () from /lib/x86_64-linux-gnu/libc.so.6
> > #2  0x00007fbf958bebf6 in ?? () from /lib/x86_64-linux-gnu/libc.so.6
> > #3  0x00007fbf958beca2 in __assert_fail () from
> /lib/x86_64-linux-gnu/libc.so.6
> > #4  0x000055ca8decd39d in bdrv_inactivate_recurse (bs=0x55ca90c80400)
> at /build/qemu-5.0/block.c:5724
> > #5  0x000055ca8dece967 in bdrv_inactivate_all () at
> /build//qemu-5.0/block.c:5792
> > #6  0x000055ca8de5539d in
> qemu_savevm_state_complete_precopy_non_iterable (inactivate_disks=true,
> in_postcopy=false, f=0x55ca907044b0)
> >     at /build/qemu-5.0/migration/savevm.c:1401
> > #7  qemu_savevm_state_complete_precopy (f=0x55ca907044b0,
> iterable_only=iterable_only@entry=false,
> inactivate_disks=inactivate_disks@entry=true)
> >     at /build/qemu-5.0/migration/savevm.c:1453
> > #8  0x000055ca8de4f581 in migration_completion (s=0x55ca8f64d9f0) at
> /build/qemu-5.0/migration/migration.c:2941
> > #9  migration_iteration_run (s=0x55ca8f64d9f0) at
> /build/qemu-5.0/migration/migration.c:3295
> > #10 migration_thread (opaque=opaque@entry=0x55ca8f64d9f0) at
> /build/qemu-5.0/migration/migration.c:3459
> > #11 0x000055ca8dfc6716 in qemu_thread_start (args=<optimized out>) at
> /build/qemu-5.0/util/qemu-thread-posix.c:519
> > #12 0x00007fbf95c5f184 in start_thread () from
> /lib/x86_64-linux-gnu/libpthread.so.0
> > #13 0x00007fbf9598cbed in clone () from /lib/x86_64-linux-gnu/libc.so.6
> >
> > When the first migration completes, bs->open_flags will set
> BDRV_O_INACTIVE
> > flag by bdrv_inactivate_all(), and during the second migration the
> > bdrv_inactivate_recurse assert that the bs->open_flags is already
> > BDRV_O_INACTIVE enabled which cause crash.
> >
> > As Vladimir suggested, this patch makes migrate_prepare check the state of
> vm and
> > return error if it is in RUN_STATE_POSTMIGRATE state.
> >
> > Signed-off-by: Tuguoyi <tu.guoyi@h3c.com>
> Similar issue is reported by Li Zhang(+CC) with almost same patch[3]
> to fix this.
> 
> Reported-by: Li Zhang <li.zhang@cloud.ionos.com>
> Reviewed-by: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
> 
> [3] https://marc.info/?l=qemu-devel&m=160749859831357&w=2
> > ---
> >  migration/migration.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 87a9b59..5e33962 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -2115,6 +2115,12 @@ static bool migrate_prepare(MigrationState *s,
> bool blk, bool blk_inc,
> >          return false;
> >      }
> >
> > +    if (runstate_check(RUN_STATE_POSTMIGRATE)) {
> > +        error_setg(errp, "Can't migrate the vm that was paused due to "
> > +                   "previous migration");
> > +        return false;
> > +    }
> > +
> >      if (migration_is_blocked(errp)) {
> >          return false;
> >      }
> > --
> > 2.7.4
> >
> > [Patch v2]:
> https://lists.gnu.org/archive/html/qemu-devel/2020-12/msg01318.html
> > [Patch v1]:
> https://lists.gnu.org/archive/html/qemu-devel/2020-11/msg05950.html