- bnc#972756 - Can't migrate HVM guest from SLES12SP1 Xen host

to SLES12SP2 Alpha 1 host using xl migrate 
  libxl.migrate-legacy-stream-read.patch

OBS-URL: https://build.opensuse.org/package/show/Virtualization/xen?expand=0&rev=419

libxl.migrate-legacy-stream-read.patch

@@ -0,0 +1,101 @@
+tools/libxl: Fix legacy migration following COLO backchannel breakage
+
+c/s f5d947bf1b "tools/libxl: add back channel support to read stream"
+made a bogus adjustment to libxl__stream_read_start(), including
+removing the comment hinting at what was going on, which breaks
+conversion of a legacy migration stream.
+
+Symptoms look like:
+
+  root@anonymi:~ # xl migrate domU host
+  migration target: Ready to receive domain.
+  Saving to migration stream new xl format (info 0x1/0x0/2677)
+  xc: error: error polling suspend notification channel: -1: Internal error
+  Loading new save file <incoming migration stream> (new xl fmt info 0x1/0x0/2677)
+   Savefile contains xl domain config in JSON format
+  Parsing config from <saved>
+  libxl: error: libxl_stream_read.c:327:stream_header_done: Invalid ident: expected 0x4c6962786c466d74, got 0x01f00f0000000000
+  libxl: error: libxl_utils.c:430:libxl_read_exactly: file/stream truncated reading ipc msg header from domain 1 save/restore helper stdout pipe
+
+The adjustment is not required for backchannel support (as there is no
+interaction between back channels and legacy conversion), and caused
+stream->fd to be latched in the datacopier before legacy conversion
+substitutes it for the fd which is the output of the conversion script.
+
+This causes libxl to consume data from the legacy stream rather than the
+v2 stream, and for the conversion script to encounter an error as the
+legacy stream appears to skip ahead.
+
+Undo the adjustments to libxl__stream_read_start(), and introduce a
+better description of what is going on.  Introduce some extra assertions
+to try and catch similar breakage in the future.
+
+Reported-by: Olaf Hering <olaf@aepfle.de>
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+---
+CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
+CC: Wei Liu <wei.liu2@citrix.com>
+CC: Olaf Hering <olaf@aepfle.de>
+CC: Yang Hongyang <hongyang.yang@easystack.cn>
+CC: Wen Congyang <wency@cn.fujitsu.com>
+CC: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
+---
+ tools/libxl/libxl_stream_read.c | 33 ++++++++++++++++++++++++---------
+ 1 file changed, 24 insertions(+), 9 deletions(-)
+
+diff --git a/tools/libxl/libxl_stream_read.c b/tools/libxl/libxl_stream_read.c
+index 9659051..89c2f21 100644
+--- a/tools/libxl/libxl_stream_read.c
++++ b/tools/libxl/libxl_stream_read.c
+@@ -234,16 +234,16 @@ void libxl__stream_read_start(libxl__egc *egc,
+     stream->running = true;
+     stream->phase   = SRS_PHASE_NORMAL;
+ 
+-    dc->ao       = stream->ao;
+-    dc->copywhat = "restore v2 stream";
+-    dc->readfd = stream->fd;
+-    dc->writefd  = -1;
+-
+-    if (stream->back_channel)
+-        return;
+-
+     if (stream->legacy) {
+-        /* Convert the legacy stream. */
++        /*
++         * Convert the legacy stream.
++         *
++         * This results in a fork()/exec() of conversion helper script.  It is
++         * passed the exiting stream->fd as an input, and returns the
++         * transformed stream via a new pipe.  The fd of this new pipe then
++         * replaces stream->fd, to make the rest of the stream read code
++         * agnostic to whether legacy conversion is happening or not.
++         */
+         libxl__conversion_helper_state *chs = &stream->chs;
+ 
+         chs->legacy_fd = stream->fd;
+@@ -258,10 +258,25 @@ void libxl__stream_read_start(libxl__egc *egc,
+             goto err;
+         }
+ 
++        /* There should be no interaction of COLO backchannels and legacy
++         * stream conversion. */
++        assert(!stream->back_channel);
++
++        /* Confirm *dc is still zeroed out, while we shuffle stream->fd. */
++        assert(dc->ao == NULL);
+         assert(stream->chs.v2_carefd);
+         stream->fd = libxl__carefd_fd(stream->chs.v2_carefd);
+         stream->dcs->libxc_fd = stream->fd;
+     }
++    /* stream->fd is now a v2 stream. */
++
++    dc->ao       = stream->ao;
++    dc->copywhat = "restore v2 stream";
++    dc->readfd   = stream->fd;
++    dc->writefd  = -1;
++
++    if (stream->back_channel)
++        return;
+ 
+     /* Start reading the stream header. */
+     rc = setup_read(stream, "stream header",

xen.changes

@@ -1,3 +1,10 @@
+-------------------------------------------------------------------
+Fri Apr 15 09:22:31 UTC 2016 - ohering@suse.de
+
+- bnc#972756 - Can't migrate HVM guest from SLES12SP1 Xen host
+  to SLES12SP2 Alpha 1 host using xl migrate 
+  libxl.migrate-legacy-stream-read.patch
+
 -------------------------------------------------------------------
 Fri Apr  1 20:14:38 UTC 2016 - jfehlig@suse.com
 

xen.spec

@@ -198,6 +198,7 @@ Source57:       xen-utils-0.1.tar.bz2
 # For xen-libs
 Source99:       baselibs.conf
 # Upstream patches
+Patch0:         libxl.migrate-legacy-stream-read.patch
 Patch164:       xsa164.patch
 # Upstream qemu-traditional patches
 Patch250:       VNC-Support-for-ExtendedKeyEvent-client-message.patch
@@ -514,6 +515,7 @@ Authors:
 %prep
 %setup -q -n %xen_build_dir -a 1 -a 2 -a 5 -a 6 -a 57
 # Upstream patches
+%patch0 -p1
 %patch164 -p1
 # Upstream qemu patches
 %patch250 -p1