assert is not async-signal-safe.
In practice the effect of calling assert there is that if the
assertion fails we might get a secondary crash, or other undesirable
behaviour from stdio (which is how assert usually reports failures).
Mention in a comment in libxl__self_pipe_wakeup that it has to be
async-signal-safe.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
This is a complicated set of changes which must be done together for
bisectability.
* libxl-save-helper is updated to unconditionally use libxc migration v2.
* libxl compatibility workarounds in libxc are disabled for save operations.
* libxl__stream_write_start() is logically spliced into the event location
where libxl__xc_domain_save() used to reside.
* Ownership of the helper state moves into stream_write_state.
* xl is updated to indicate that the stream is now v2
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
v4:
* Don't use _init() needlessly
v3: Many small changes, follwing similar review to the restore side
This is a complicated set of changes which must be done together for
bisectability.
* libxl-save-helper is updated to unconditionally use libxc migration
v2.
* libxl compatibility workarounds in libxc are disabled for restore
operations.
* libxl__stream_read_start() is logically spliced into the event
location where libxl__xc_domain_restore() used to reside.
* Ownership of the save_helper_state moves to stream_read_state.
The parameters 'hvm', 'pae', and 'superpages' were previously
superfluous, and are completely unused in migration
v2. callbacks->toolstack_restore is handled via a migration v2 record
now, rather than via a callback from libxc.
NB: this change breaks Remus. Further untangling needs to happen
before Remus will function.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
v4:
* Don't use _init() needlessly
v3:
* Simplify from v2.
* Alter the ownership of save_helper_state
v2:
* Drop "legacy_width" from the IDL
* Gain a LIBXL_HAVE_ to signify support of migration v2 streams
During startup of the save/restore helper, set the disposition of
SIGTERM appropriately.
For restore, we can simply die immediately - there is no point trying
to do any kind of cleanup on what is now going to be a trashed domain.
For save, we want to arrange that libxc's cleanup code (eg turning off
logdirty) takes place. So our signal handler replaces the fd with one
on which writes will fail, causing libxc's own loop to fail next time
it actually tries to do a write.
Currently this has only a minor beneficial effect: we don't send the
helper a SIGTERM ourselves, and if someone else contrives to send our
helper a SIGTERM they have probably sent one to libxl too in which
case things are going to be a bit messy anyway.
But in the next patch libxl itself is going to use SIGTERM to
implement ao abort requests.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
v2: New in this version of the series.
Two unrelated non-functional changes, broken out into a pre-patch for
easier review:
Break out a function sendsig() in libxl_save_callout.c.
Move io_fd to be a global variable in libxl_save_helper.c.
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
v2: New in this version of the series.
The VM generation ID support in libxc/libxl was based on a draft
specification which subsequently changed considerably. Remove much of
the code in anticipation of introducing something simpler that
conforms to the current specification from Microsoft.
Switch to using a HVM param (HVM_PARAM_VM_GENERATION_ID_ADDR) instead
of the hvmloader/generation-id-address XenStore key. This simplifies
save/restore since it only needs to transfer the value of this param.
There are no changes to the migration stream format or the public
libxl API.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
[ ijc -- updated xc_nomigrate.c for interface change ]
Commit b327a3f421 moved the rewinding of
toolstack_save_fd to libxl. This breaks remus, because in remus mode,
toolstack_save_cb will be called in every checkpoint, and if we don't
rewind it in libxl_save_helper, it will surely fail.
This fix is just a hack: in fact the whole toolstack save thing should
be done in libxl. But for now (until migration v2) this fix should
solve both remus and Jason Adryuk's use case.
Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
Tested-by: Jason Andryuk <andryuk@aero.org>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
toolstack_save data is written to a temporary file in libxl and read
back in libxl-save-helper. The file position must be reset prior to
reading the file, which is done in libxl-save-helper with lseek.
lseek is unsupported for pipes and sockets, so a wrapper passing such an
fd to libxl-save-helper fails the lseek. Moving the lseek to libxl
avoids the error, allowing the save to continue.
Signed-off-by: Jason Andryuk <andryuk@aero.org>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Fix two unfree()'d allocations in libxl-save-helper, to get them out of the
way of other legitimate complaints from valgrind.
The first is easy; close the interface to libxc when done with it.
The second can be fixed by removing the complexity of creating the logging
instance. Initialise the global 'logger' in place rather than as an
allocation, which requires changing the indirection of its use in 5 locations.
struct xentoollog_logger_tellparent and function createlogger_tellparent() are
now unused and removed.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Commit 00a4b65f85 Sep 7 2010
"libxc: provide notification of final checkpoint to restore end"
broke migration from any version of Xen using tools from prior to that commit
Older tools have no idea about an XC_SAVE_ID_LAST_CHECKPOINT, causing newer
tools xc_domain_restore() to start reading the qemu save record, as
ctx->last_checkpoint is 0.
The failure looks like:
xc: error: Max batch size exceeded (1970103633). Giving up.
where 1970103633 = 0x756d6551 = *(uint32_t*)"Qemu"
With this fix in place, the behaviour for normal migrations is reverted to how
it was before the regression; the migration is considered non-checkpointed
right from the start. A XC_SAVE_ID_LAST_CHECKPOINT chunk seen in the
migration stream is a nop. For checkpointed migrations the behaviour is
unchanged.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
Acked-by: Shriram Rajagopalan <rshriram@cs.ubc.ca> (Remus bits)
libxenctrl expects to be able to simply run the save or restore
operation synchronously. This won't work well in a process which is
trying to handle multiple domains.
The options are:
- Block such a whole process (eg, the whole of libvirt) while
migration completes (or until it fails).
- Create a thread to run xc_domain_save and xc_domain_restore on.
This is quite unpalatable. Multithreaded programming is error
prone enough without generating threads in libraries, particularly
if the thread does some very complex operation.
- Fork and run the operation in the child without execing. This is
no good because we would need to negotiate with the caller about
fds we would inherit (and we might be a very large process).
- Fork and exec a helper.
Of these options the latter is the most palatable.
Consequently:
* A new helper program libxl-save-helper (which does both save and
restore). It will be installed in /usr/lib/xen/bin. It does not
link against libxl, only libxc, and its error handling does not
need to be very advanced. It does contain a plumbing through of
the logging interface into the callback stream.
* A small ad-hoc protocol between the helper and libxl which allows
log messages and the libxc callbacks to be passed up and down.
Protocol doc comment is in libxl_save_helper.c.
* To avoid a lot of tedium the marshalling boilerplate (stubs for the
helper and the callback decoder for libxl) is generated with a
small perl script.
* Implement new functionality to spawn the helper, monitor its
output, provide responses, and check on its exit status.
* The functions libxl__xc_domain_restore_done and
libxl__xc_domain_save_done now turn out to want be called in the
same place. So make their state argument a void* so that the two
functions are type compatible.
The domain save path still writes the qemu savefile synchronously.
This will need to be fixed in a subsequent patch.
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Ian Jackson
Andrew Cooper
David Vrabel
Yang Hongyang
Jason Andryuk