Rate limiting sleeps the migration thread for a while when it runs
out of bandwidth; but sometimes we want to wake up to get on with
something more urgent (like a postcopy request).  Here we use
a semaphore with a timedwait instead of a simple sleep; Incrementing
the sempahore will wake it up sooner.  Anything that consumes
these urgent events must decrement the sempahore.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20180613102642.23995-3-dgilbert@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

When cancel migration during RDMA precopy, the source qemu main thread hangs sometime.

The backtrace is:
    (gdb) bt
    #0  0x00007f249eabd43d in write () from /lib64/libpthread.so.0
    #1  0x00007f24a1ce98e4 in rdma_get_cm_event (channel=0x4675d10, event=0x7ffe2f643dd0) at src/cma.c:2189
    #2  0x00000000007b6166 in qemu_rdma_cleanup (rdma=0x6784000) at migration/rdma.c:2296
    #3  0x00000000007b7cae in qio_channel_rdma_close (ioc=0x3bfcc30, errp=0x0) at migration/rdma.c:2999
    #4  0x00000000008db60e in qio_channel_close (ioc=0x3bfcc30, errp=0x0) at io/channel.c:273
    #5  0x00000000007a8765 in channel_close (opaque=0x3bfcc30) at migration/qemu-file-channel.c:98
    #6  0x00000000007a71f9 in qemu_fclose (f=0x527c000) at migration/qemu-file.c:334
    #7  0x0000000000795b96 in migrate_fd_cleanup (opaque=0x3b46280) at migration/migration.c:1162
    #8  0x000000000093a71b in aio_bh_call (bh=0x3db7a20) at util/async.c:90
    #9  0x000000000093a7b2 in aio_bh_poll (ctx=0x3b121c0) at util/async.c:118
    #10 0x000000000093f2ad in aio_dispatch (ctx=0x3b121c0) at util/aio-posix.c:436
    #11 0x000000000093ab41 in aio_ctx_dispatch (source=0x3b121c0, callback=0x0, user_data=0x0)
        at util/async.c:261
    #12 0x00007f249f73c7aa in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
    #13 0x000000000093dc5e in glib_pollfds_poll () at util/main-loop.c:215
    #14 0x000000000093dd4e in os_host_main_loop_wait (timeout=28000000) at util/main-loop.c:263
    #15 0x000000000093de05 in main_loop_wait (nonblocking=0) at util/main-loop.c:522
    #16 0x00000000005bc6a5 in main_loop () at vl.c:1944
    #17 0x00000000005c39b5 in main (argc=56, argv=0x7ffe2f6443f8, envp=0x3ad0030) at vl.c:4752

It does not get the RDMA_CM_EVENT_DISCONNECTED event after rdma_disconnect sometime.

According to IB Spec once active side send DREQ message, it should wait for DREP message
and only once it arrived it should trigger a DISCONNECT event. DREP message can be dropped
due to network issues.
For that case the spec defines a DREP_timeout state in the CM state machine, if the DREP is
dropped we should get a timeout and a TIMEWAIT_EXIT event will be trigger.
Unfortunately the current kernel CM implementation doesn't include the DREP_timeout state
and in above scenario we will not get DISCONNECT or TIMEWAIT_EXIT events.

So it should not invoke rdma_get_cm_event which may hang forever, and the event channel
is also destroyed in qemu_rdma_cleanup.
Signed-off-by: NLidong Chen <lidongchen@tencent.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

After we updated the dirty bitmaps of ramblocks, we also need to update
the critical fields in RAMState to make sure it is ready for a resume.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-18-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

This patch implements the first part of core RAM resume logic for
postcopy. ram_resume_prepare() is provided for the work.

When the migration is interrupted by network failure, the dirty bitmap
on the source side will be meaningless, because even the dirty bit is
cleared, it is still possible that the sent page was lost along the way
to destination. Here instead of continue the migration with the old
dirty bitmap on source, we ask the destination side to send back its
received bitmap, then invert it to be our initial dirty bitmap.

The source side send thread will issue the MIG_CMD_RECV_BITMAP requests,
once per ramblock, to ask for the received bitmap. On destination side,
MIG_RP_MSG_RECV_BITMAP will be issued, along with the requested bitmap.
Data will be received on the return-path thread of source, and the main
migration thread will be notified when all the ramblock bitmaps are
synchronized.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-17-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

This is hook function to be called when a postcopy migration wants to
resume from a failure. For each module, it should provide its own
recovery logic before we switch to the postcopy-active state.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-16-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Creating new message to reply for MIG_CMD_POSTCOPY_RESUME. One uint32_t
is used as payload to let the source know whether destination is ready
to continue the migration.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-15-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Introducing this new command to be sent when the source VM is ready to
resume the paused migration.  What the destination does here is
basically release the fault thread to continue service page faults.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-14-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Introducing new return path message MIG_RP_MSG_RECV_BITMAP to send
received bitmap of ramblock back to source.

This is the reply message of MIG_CMD_RECV_BITMAP, it contains not only
the header (including the ramblock name), and it was appended with the
whole ramblock received bitmap on the destination side.

When the source receives such a reply message (MIG_RP_MSG_RECV_BITMAP),
it parses it, convert it to the dirty bitmap by inverting the bits.

One thing to mention is that, when we send the recv bitmap, we are doing
these things in extra:

- converting the bitmap to little endian, to support when hosts are
  using different endianess on src/dst.

- do proper alignment for 8 bytes, to support when hosts are using
  different word size (32/64 bits) on src/dst.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-13-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Add a new vm command MIG_CMD_RECV_BITMAP to request received bitmap for
one ramblock.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-12-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Allows the fault thread to stop handling page faults temporarily. When
network failure happened (and if we expect a recovery afterwards), we
should not allow the fault thread to continue sending things to source,
instead, it should halt for a while until the connection is rebuilt.

When the dest main thread noticed the failure, it kicks the fault thread
to switch to pause state.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-7-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Let the thread pause for network issues.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-6-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

When there is IO error on the incoming channel (e.g., network down),
instead of bailing out immediately, we allow the dst vm to switch to the
new POSTCOPY_PAUSE state. Currently it is still simple - it waits the
new semaphore, until someone poke it for another attempt.

One note is that here on ram loading thread we cannot detect the
POSTCOPY_ACTIVE state, but we need to detect the more specific
POSTCOPY_INCOMING_RUNNING state, to make sure we have already loaded all
the device states.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-5-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Now when network down for postcopy, the source side will not fail the
migration. Instead we convert the status into this new paused state, and
we will try to wait for a rescue in the future.

If a recovery is detected, migration_thread() will reset its local
variables to prepare for that.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-4-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Postcopy total blocktime is available on destination side only.
But query-migrate was possible only for source. This patch
adds ability to call query-migrate on destination.
To be able to see postcopy blocktime, need to request postcopy-blocktime
capability.

The query-migrate command will show following sample result:
{"return":
    "postcopy-vcpu-blocktime": [115, 100],
    "status": "completed",
    "postcopy-blocktime": 100
}}

postcopy_vcpu_blocktime contains list, where the first item is the first
vCPU in QEMU.

This patch has a drawback, it combines states of incoming and
outgoing migration. Ongoing migration state will overwrite incoming
state. Looks like better to separate query-migrate for incoming and
outgoing migration or add parameter to indicate type of migration.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1521742647-25550-7-git-send-email-a.perevalov@samsung.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

This patch provides blocktime calculation per vCPU,
as a summary and as a overlapped value for all vCPUs.

This approach was suggested by Peter Xu, as an improvements of
previous approch where QEMU kept tree with faulted page address and cpus bitmask
in it. Now QEMU is keeping array with faulted page address as value and vCPU
as index. It helps to find proper vCPU at UFFD_COPY time. Also it keeps
list for blocktime per vCPU (could be traced with page_fault_addr)

Blocktime will not calculated if postcopy_blocktime field of
MigrationIncomingState wasn't initialized.
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1521742647-25550-4-git-send-email-a.perevalov@samsung.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

Cause the vhost-user client to be woken up whenever:
  a) We place a page in postcopy mode
  b) We get a fault and the page has already been received
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Provide a helper to send a 'wake' request on a userfaultfd for
a shared process.
The address in the clients address space is specified together
with the RAMBlock it was resolved to.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Provide a helper to be used by shared waker functions to request
shared pages from the source.
The last_rb pointer is moved into the incoming state since this
helper can update it as well as the main fault thread function.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Allow other userfaultfd's to be registered into the fault thread
so that handlers for shared memory can get responses.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Postcopy migration of dirty bitmaps. Only named dirty bitmaps are migrated.

If destination qemu is already containing a dirty bitmap with the same name
as a migrated bitmap (for the same node), then, if their granularities are
the same the migration will be done, otherwise the error will be generated.

If destination qemu doesn't contain such bitmap it will be created.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 20180313180320.339796-12-vsementsov@virtuozzo.com
[Changed '+' to '*' as per list discussion. --js]
Signed-off-by: NJohn Snow <jsnow@redhat.com>

There would be savevm states (dirty-bitmap) which can migrate only in
postcopy stage. The corresponding pending is introduced here.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: 20180313180320.339796-6-vsementsov@virtuozzo.com

Route async errors (especially from sockets) down through
migration_channel_connect and on to migrate_fd_connect where they
can be cleaned up.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

This reverts commits
ca6011c2 migration: add postcopy total blocktime into query-migrate
5f32dc8e migration: add blocktime calculation into migration-test
2f7dae9d migration: postcopy_blocktime documentation
3be98be4 migration: calculate vCPU blocktime on dst side
01a87f0b migration: add postcopy blocktime ctx into MigrationIncomingState
31bf06a9 migration: introduce postcopy-blocktime capability

as they don't build on ppc32 due to trying to do atomic accesses
on types that are larger than the host pointer type.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

Postcopy total blocktime is available on destination side only.
But query-migrate was possible only for source. This patch
adds ability to call query-migrate on destination.
To be able to see postcopy blocktime, need to request postcopy-blocktime
capability.

The query-migrate command will show following sample result:
{"return":
    "postcopy-vcpu-blocktime": [115, 100],
    "status": "completed",
    "postcopy-blocktime": 100
}}

postcopy_vcpu_blocktime contains list, where the first item is the first
vCPU in QEMU.

This patch has a drawback, it combines states of incoming and
outgoing migration. Ongoing migration state will overwrite incoming
state. Looks like better to separate query-migrate for incoming and
outgoing migration or add parameter to indicate type of migration.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

This patch provides blocktime calculation per vCPU,
as a summary and as a overlapped value for all vCPUs.

This approach was suggested by Peter Xu, as an improvements of
previous approch where QEMU kept tree with faulted page address and cpus bitmask
in it. Now QEMU is keeping array with faulted page address as value and vCPU
as index. It helps to find proper vCPU at UFFD_COPY time. Also it keeps
list for blocktime per vCPU (could be traced with page_fault_addr)

Blocktime will not calculated if postcopy_blocktime field of
MigrationIncomingState wasn't initialized.
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

Check the return value of pre_save state and fail vmstate_save_state
if the pre_save failed.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20170925112917.21340-3-dgilbert@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

Strings are more readable for debugging.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <1504081950-2528-5-git-send-email-peterx@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
  Fixed up merge with 977c73

The only exception are groups of numers separated by symbols
'.', ' ', ':', '/', like 'ab.09.7d'.

This patch is made by the following:

> find . -name trace-events | xargs python script.py

where script.py is the following python script:
=========================
 #!/usr/bin/env python

import sys
import re
import fileinput

rhex = '%[-+ *.0-9]*(?:[hljztL]|ll|hh)?(?:x|X|"\s*PRI[xX][^"]*"?)'
rgroup = re.compile('((?:' + rhex + '[.:/ ])+' + rhex + ')')
rbad = re.compile('(?<!0x)' + rhex)

files = sys.argv[1:]

for fname in files:
    for line in fileinput.input(fname, inplace=True):
        arr = re.split(rgroup, line)
        for i in range(0, len(arr), 2):
            arr[i] = re.sub(rbad, '0x\g<0>', arr[i])

        sys.stdout.write(''.join(arr))
=========================
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Acked-by: NCornelia Huck <cohuck@redhat.com>
Message-id: 20170731160135.12101-5-vsementsov@virtuozzo.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

With the move of some docs/ to docs/devel/ on ac06724a,
no references were updated.
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

We need to do things at load time and at cleanup time.
Signed-off-by: NJuan Quintela <quintela@redhat.com>

--

Move the printing of the error message so we can print the device
giving the error.
Add call to postcopy stuff
Message-Id: <20170628095228.4661-4-quintela@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

We are going to use it now for more than save live regions.
Once there rename qemu_savevm_state_begin() to qemu_savevm_state_setup().
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20170628095228.4661-2-quintela@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

There are some places that binded "return path" with postcopy. Let's be
prepared for its usage even without postcopy. This patch mainly did this
on source side.
Signed-off-by: NPeter Xu <peterx@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

A couple more traces that would have made fixing that postcopy
bug a bit easier.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

We use an unsigned long for the page number.  Notice that our bitmaps
already got that for the index, so we have that limit.
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

--

rename page to page_abs everywhere.
fix trace types for pages

Create ram_block_discard_range in exec.c to replace
postcopy_ram_discard_range and most of ram_discard_range.

Those two routines are a bit of a weird combination, and
ram_discard_range is about to get more complex for hugepages.
It's OS dependent code (so shouldn't be in migration/ram.c) but
it needs quite a bit of the innards of RAMBlock so doesn't belong in
the os*.c.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NLaurent Vivier <lvivier@redhat.com>
Message-Id: <20170224182844.32452-5-dgilbert@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

There are a number of unused trace events that
scripts/cleanup-trace-events.pl finds.  The "hw/vfio/pci-quirks.c"
filename was typoed and "qapi/qapi-visit-core.c" was missing the qapi/
directory prefix.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 20170126171613.1399-3-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Add some tracing to vmstate_subsection_save and vmstate_save_state
to help in debugging when you're not sure if a conditional piece
of data is being saved.

In vmstate_subsection_save I renamed the inner vmsd to avoid the aliasing
and be able to print both names.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20161212125838.14425-1-dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

So we can remove DPRINTF() macro
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1485207141-1941-2-git-send-email-quintela@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
  Fixed up 'remained/remaining' as requested by Eric

Currently we cannot directly transfer a QTAILQ instance because of the
limitation in the migration code. Here we introduce an approach to
transfer such structures. We created VMStateInfo vmstate_info_qtailq
for QTAILQ. Similar VMStateInfo can be created for other data structures
such as list.

When a QTAILQ is migrated from source to target, it is appended to the
corresponding QTAILQ structure, which is assumed to have been properly
initialized.

This approach will be used to transfer pending_events and ccs_list in spapr
state.

We also create some macros in qemu/queue.h to access a QTAILQ using pointer
arithmetic. This ensures that we do not depend on the implementation
details about QTAILQ in the migration code.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NJianjun Duan <duanj@linux.vnet.ibm.com>
Message-Id: <1484852453-12728-3-git-send-email-duanj@linux.vnet.ibm.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

When handling failover, COLO processes differently according to
the different stage of failover process, here we introduce a global
atomic variable to record the status of failover.

We add four failover status to indicate the different stage of failover process.
You should use the helpers to get and set the value.
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NAmit Shah <amit.shah@redhat.com>
Signed-off-by: NAmit Shah <amit@amitshah.net>