Re: [Qemu-devel] HEAD is failing virt-test on migration tests

[Lucas Meneghel Rodrigues]

On Fri, Feb 13, 2015 at 9:18 AM, Alexander Graf <address@hidden> wrote:
> On 13.02.15 10:04, Dr. David Alan Gilbert wrote:
> >  * Alexander Graf (address@hidden) wrote:
> > >  On 13.02.15 01:29, Lucas Meneghel Rodrigues wrote:
> > > >  Copying Alex.
> > > >
> > > >  OK, after bisecting, this is what I've got:
> > > >
> > > >  8118f0950fc77cce7873002a5021172dd6e040b5 is the first bad commit
> > > >  commit 8118f0950fc77cce7873002a5021172dd6e040b5
> > > >  Author: Alexander Graf <address@hidden <mailto:address@hidden>>
> > > >  Date:   Thu Jan 22 15:01:39 2015 +0100
> > > >
> > > >      migration: Append JSON description of migration stream
> > > >
> > > >      One of the annoyances of the current migration format is the 
> > > > fact that
> > > >      it's not self-describing. In fact, it's not properly 
> > > > describing at all.
> > > >      Some code randomly scattered throughout QEMU elaborates 
> > > > roughly how to
> > > >      read and write a stream of bytes.
> > > >
> > > >      We discussed an idea during KVM Forum 2013 to add a JSON 
> > > > description of
> > > >      the migration protocol itself to the migration stream. This 
> > > > patch
> > > >      adds a section after the VM_END migration end marker that 
> > > > contains
> > > >      description data on what the device sections of the stream are
> > > >  composed of.
> > > >
> > > >      This approach is backwards compatible with any QEMU version 
> > > > reading the
> > > >      stream, because QEMU just stops reading after the VM_END 
> > > > marker and
> > > >  ignores
> > > >      any data following it.
> > > >
> > > >      With an additional external program this allows us to 
> > > > decipher the
> > > >      contents of any migration stream and hopefully make migration 
> > > > bugs
> > > >  easier
> > > >      to track down.
> > > >
> > > >      Signed-off-by: Alexander Graf <address@hidden 
> > > > <mailto:address@hidden>>
> > > >      Signed-off-by: Amit Shah <address@hidden
> > > >  <mailto:address@hidden>>
> > > >      Signed-off-by: Juan Quintela <address@hidden
> > > >  <mailto:address@hidden>>
> > > >
> > > >  :040000 040000 e9a8888ac242a61fbd05bbb0daa3e8877970e738
> > > >  61df81f831bc86b29f65883523ea95abb36f1ec5 Mhw
> > > >  :040000 040000 fe0659bed17d86c43657c26622d64fd44a1af037
> > > >  7092a6b6515a3d0077f68ff2d80dbd74597a244f Minclude
> > > >  :040000 040000 d90d6f1fe839abf21a45eaba5829d5a6a22abeb1
> > > >  c2b1dcda197d96657458d699c185e39ae45f3c6c Mmigration
> > > >  :100644 100644 98895fee81edfbc659fc42d467e930d06b1afa7d
> > > >  80407662ad3ed860d33a9d35f5c44b1d19c4612b Msavevm.c
> > > >  :040000 040000 cf218bc2b841cd51ebe3972635be2cfbb1de9dfa
> > > >  7aaf3d10ef7f73413b228e854fe6f04317151e46 Mtests
> > > >
> > > >  So there you go. I'm going to sleep, if you need any extra help 
> > > > let me know.
> > >
> > >  So the major difference with this patch applied is that the sender 
> > > could
> > >  send more data than the receive wants to read. I can't see the 
> > > actual
> > >  migrate command you used down there.
> > >
> > >  I haven't seen this actually being a problem so far, as the 
> > > receiver
> > >  just close()s its file descriptor once it hits VM_EOF. This should 
> > > only
> > >  break senders if they expect they can send more. That said, I 
> > > think I
> > >  only tested offline migration (via exec:), so maybe QEMU is 
> > > behaving
> > >  badly and actually wants to send all data and just fails the 
> > > migration
> > >  without?
> >
> >  Hmm, for such an odd change to the migration stream it's a surprise 
> > you
> >  didn't test it live.
>
> Well, let's say I don't remember explicitly testing it live - I 
> probably
> did at one point.
>
> I just verified that migrating with tcp:... works fine in master.

It is working fine with tcp migration in master indeed. The thing is, 
virt-test tests a bunch of variants, among them fd. fd is the only one 
failing from the list of things we do test (which also happen to be the 
virt-test default test set).

> Alex