Re: s390 migration crash

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Mar 21, 2023 at 08:19:00PM -0400, Peter Xu wrote:
> On Tue, Mar 21, 2023 at 08:24:37PM +0000, Dr. David Alan Gilbert wrote:
> > Hi Peter's,
> >   Peter M pointed me to a seg in a migration test in CI; I can reproduce
> > it:
> >   * On an s390 host
> 
> How easy to reproduce?
> 
> >   * only as part of a make check - running migration-test by itself
> > doesn't trigger for me.
> >   * It looks like it's postcopy preempt

snip

> > Looking at the iov and file it's garbage; so it makes me think this is
> > something like a flush on a closed file.
> 
> I didn't figure out how that could be closed, but I think there's indeed a
> possible race that the qemufile can be accessed by both the return path
> thread and the migration thread concurrently, while qemufile is not thread
> safe on that.

snip

> From 0e317fa78e9671c119f6be78a0e0a36201517dc2 Mon Sep 17 00:00:00 2001
> From: Peter Xu <peterx@redhat.com>
> Date: Tue, 21 Mar 2023 19:58:42 -0400
> Subject: [PATCH 1/2] io: tls: Inherit QIO_CHANNEL_FEATURE_SHUTDOWN on server
>  side
> 
> TLS iochannel will inherit io_shutdown() from the master ioc, however we
> missed to do that on the server side.
> 
> This will e.g. allow qemu_file_shutdown() to work on dest QEMU too for
> migration.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  io/channel-tls.c | 3 +++
>  1 file changed, 3 insertions(+)

Acked-by: Daniel P. Berrangé <berrange@redhat.com>

> 
> diff --git a/io/channel-tls.c b/io/channel-tls.c
> index 5a7a3d48d6..9805dd0a3f 100644
> --- a/io/channel-tls.c
> +++ b/io/channel-tls.c
> @@ -74,6 +74,9 @@ qio_channel_tls_new_server(QIOChannel *master,
>      ioc = QIO_CHANNEL_TLS(object_new(TYPE_QIO_CHANNEL_TLS));
>  
>      ioc->master = master;
> +    if (qio_channel_has_feature(master, QIO_CHANNEL_FEATURE_SHUTDOWN)) {
> +        qio_channel_set_feature(QIO_CHANNEL(ioc), QIO_CHANNEL_FEATURE_SHUTDOWN);
> +    }
>      object_ref(OBJECT(master));
>  
>      ioc->session = qcrypto_tls_session_new(



With regards,
Daniel
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