Xen 2016/11/02

# gpg: Signature made Wed 02 Nov 2016 07:28:40 PM GMT
# gpg:                using RSA key 0x894F8F4870E1AE90
# gpg: Good signature from "Stefano Stabellini <sstabellini@kernel.org>"
# gpg:                 aka "Stefano Stabellini <stefano.stabellini@eu.citrix.com>"
# Primary key fingerprint: D04E 33AB A51F 67BA 07D3  0AEA 894F 8F48 70E1 AE90

* sstabellini/tags/xen-20161102-tag:
  PCMachineState: introduce acpi_build_enabled field
  hw/xen/xen_pvdev: Include qemu/log.h for qemu_log_vprintf()

Message-id: alpine.DEB.2.10.1611021227530.19454@sstabellini-ThinkPad-X260
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

* NBD bugfix (Changlong)
* NBD write zeroes support (Eric)
* Memory backend fixes (Haozhong)
* Atomics fix (Alex)
* New AVX512 features (Luwei)
* "make check" logging fix (Paolo)
* Chardev refactoring fallout (Paolo)
* Small checkpatch improvements (Paolo, Jeff)

# gpg: Signature made Wed 02 Nov 2016 08:31:11 AM GMT
# gpg:                using RSA key 0xBFFBD25F78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream: (30 commits)
  main-loop: Suppress I/O thread warning under qtest
  docs/rcu.txt: Fix minor typo
  vl: exit qemu on guest panic if -no-shutdown is not set
  checkpatch: allow spaces before parenthesis for 'coroutine_fn'
  x86: add AVX512_4VNNIW and AVX512_4FMAPS features
  slirp: fix CharDriver breakage
  qemu-char: do not forward events through the mux until QEMU has started
  nbd: Implement NBD_CMD_WRITE_ZEROES on client
  nbd: Implement NBD_CMD_WRITE_ZEROES on server
  nbd: Improve server handling of shutdown requests
  nbd: Refactor conversion to errno to silence checkpatch
  nbd: Support shorter handshake
  nbd: Less allocation during NBD_OPT_LIST
  nbd: Let client skip portions of server reply
  nbd: Let server know when client gives up negotiation
  nbd: Share common option-sending code in client
  nbd: Send message along with server NBD_REP_ERR errors
  nbd: Share common reply-sending code in server
  nbd: Rename struct nbd_request and nbd_reply
  nbd: Rename NbdClientSession to NBDClientSession
  ...
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

virtio, pc: fixes and features

nvdimm hotplug support
virtio migration and ioeventfd rework
virtio crypto device
ipmi fixes
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

# gpg: Signature made Tue 01 Nov 2016 05:23:40 PM GMT
# gpg:                using RSA key 0x281F0DB8D28D5469
# gpg: Good signature from "Michael S. Tsirkin <mst@kernel.org>"
# gpg:                 aka "Michael S. Tsirkin <mst@redhat.com>"
# Primary key fingerprint: 0270 606B 6F3C DF3D 0B17  0970 C350 3912 AFBE 8E67
#      Subkey fingerprint: 5D09 FD08 71C8 F85B 94CA  8A0D 281F 0DB8 D28D 5469

* remotes/mst/tags/for_upstream: (47 commits)
  acpi: fix assert failure caused by commit 35c5a52d
  acpi/ipmi: Initialize the fwinfo before fetching it
  ipmi: Add graceful shutdown handling to the external BMC
  ipmi: fix build config variable name for ipmi_bmc_extern.o
  ipmi: Implement shutdown via ACPI overtemp
  ipmi: chassis poweroff should use qemu_system_shutdown_request()
  ipmi_bmc_sim: Remove an unnecessary mutex
  ipmi: Remove hotplug from IPMI BMCs
  pc: memhp: enable nvdimm device hotplug
  nvdimm acpi: introduce _FIT
  nvdimm acpi: introduce fit buffer
  nvdimm acpi: prebuild nvdimm devices for available slots
  nvdimm acpi: use common macros instead of magic names
  acpi nvdimm: rename result_size to dsm_out_buf_siz
  nvdimm acpi: compile nvdimm acpi code arch-independently
  acpi nvdimm: fix Arg6 usage
  acpi nvdimm: fix ARG3 conflict
  acpi nvdimm: fix device physical address base
  acpi nvdimm: fix OperationRegion definition
  acpi nvdimm: fix wrong buffer size returned by DSM method
  ...
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Introduce this field to control whether ACPI build is enabled by a
particular machine or accelerator.

It defaults to true if the machine itself supports ACPI build. Xen
accelerator will disable it because Xen is in charge of building ACPI
tables for the guest.
Signed-off-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NStefano Stabellini <sstabellini@kernel.org>
Reviewed-by: NStefano Stabellini <sstabellini@kernel.org>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Tested-by: NSander Eikelenboom <linux@eikelenboom.it>

Olaf Hering reported a build failure due to an undefined reference
to 'qemu_log_vprintf'. Explicitely including qemu/log.h seems to
fix the issue.
Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NStefano Stabellini <sstabellini@kernel.org>
Acked-by: NStefano Stabellini <sstabellini@kernel.org>
Tested-by: NOlaf Hering <olaf@aepfle.de>

We do not want to display the "I/O thread spun" warning for test cases
that run under qtest. The first attempt for this (commit
01c22f2c) tested whether qtest_enabled()
was true.

Commit 21a24302 correctly recognized
that just testing qtest_enabled() is not sufficient since there are some
tests that do not use the qtest accelerator but just the qtest character
device, and thus replaced qtest_enabled() by qtest_driver().

However, there are also some tests that only use the qtest accelerator
and not the qtest chardev; perhaps most notably the bash iotests.
Therefore, we have to check both qtest_enabled() and qtest_driver().
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-Id: <20161017180939.27912-1-mreitz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

s/presented/prevented/
Signed-off-by: NPranith Kumar <bobby.prani@gmail.com>
Message-Id: <20161018050418.4912-1-bobby.prani@gmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

For automated testing purposes it can be helpful to exit qemu
(poweroff) when the guest panics. Make this the default unless
-no-shutdown is specified.

For internal-errors like errors from KVM_RUN the behaviour is
not changed, in other words QEMU does not exit to allow debugging
in the QEMU monitor.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Message-Id: <1476775794-108012-1-git-send-email-borntraeger@de.ibm.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Signed-off-by: NJeff Cody <jcody@redhat.com>
Message-Id: <83b0fae0728906e18849c971d22d077d7fc0f179.1478010883.git.jcody@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The spec can be found in Intel Software Developer Manual or in
Instruction Set Extensions Programming Reference.
Signed-off-by: NPiotr Luc <piotr.luc@intel.com>
Signed-off-by: NLuwei Kang <luwei.kang@intel.com>
Message-Id: <1477902446-5932-1-git-send-email-he.chen@linux.intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

SLIRP expects a CharBackend as the third argument to slirp_add_exec,
but net/slirp.c was passing a CharDriverState.  Fix this to restore
guestfwd functionality.
Reported-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Otherwise, the CHR_EVENT_OPENED event is sent twice: first when the
backend (for example "stdio") is opened, and second after processing
the command line.

The incorrect sending of the event prints the monitor banner when
QEMU is started with "-serial mon:stdio".  This includes the "(qemu)"
prompt; thus the monitor seems to be dead, whereas actually the
active front-end is the serial port.
Reported-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Tested-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Upstream NBD protocol recently added the ability to efficiently
write zeroes without having to send the zeroes over the wire,
along with a flag to control whether the client wants a hole.

The generic block code takes care of falling back to the obvious
write of lots of zeroes if we return -ENOTSUP because the server
does not have WRITE_ZEROES.

Ideally, since NBD_CMD_WRITE_ZEROES does not involve any data
over the wire, we want to support transactions that are much
larger than the normal 32M limit imposed on NBD_CMD_WRITE.  But
the server may still have a limit smaller than UINT_MAX, so
until experimental NBD protocol additions for advertising various
command sizes is finalized (see [1], [2]), for now we just stick to
the same limits as normal writes.

[1] https://github.com/yoe/nbd/blob/extension-info/doc/proto.md
[2] https://sourceforge.net/p/nbd/mailman/message/35081223/Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-17-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Upstream NBD protocol recently added the ability to efficiently
write zeroes without having to send the zeroes over the wire,
along with a flag to control whether the client wants to allow
a hole.

Note that when it comes to requiring full allocation, vs.
permitting optimizations, the NBD spec intentionally picked a
different sense for the flag; the rules in qemu are:
MAY_UNMAP == 0: must write zeroes
MAY_UNMAP == 1: may use holes if reads will see zeroes

while in NBD, the rules are:
FLAG_NO_HOLE == 1: must write zeroes
FLAG_NO_HOLE == 0: may use holes if reads will see zeroes

In all cases, the 'may use holes' scenario is optional (the
server need not use a hole, and must not use a hole if
subsequent reads would not see zeroes).
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-16-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

NBD commit 6d34500b clarified how clients and servers are supposed
to behave before closing a connection. It added NBD_REP_ERR_SHUTDOWN
(for the server to announce it is about to go away during option
haggling, so the client should quit sending NBD_OPT_* other than
NBD_OPT_ABORT) and ESHUTDOWN (for the server to announce it is about
to go away during transmission, so the client should quit sending
NBD_CMD_* other than NBD_CMD_DISC).  It also clarified that
NBD_OPT_ABORT gets a reply, while NBD_CMD_DISC does not.

This patch merely adds the missing reply to NBD_OPT_ABORT and teaches
the client to recognize server errors.  Actually teaching the server
to send NBD_REP_ERR_SHUTDOWN or ESHUTDOWN would require knowing that
the server has been requested to shut down soon (maybe we could do
that by installing a SIGINT handler in qemu-nbd, which transitions
from RUNNING to a new state that waits for the client to react,
rather than just out-right quitting - but that's a bigger task for
another day).
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-15-git-send-email-eblake@redhat.com>
[Move dummy ESHUTDOWN to include/qemu/osdep.h. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Checkpatch complains that 'return EINVAL' is usually wrong
(since we tend to favor 'return -EINVAL').  But it is a
false positive for nbd_errno_to_system_errno().  Since NBD
may add future defined wire values, refactor the code to
keep checkpatch happy.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-14-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The NBD Protocol allows the server and client to mutually agree
on a shorter handshake (omit the 124 bytes of reserved 0), via
the server advertising NBD_FLAG_NO_ZEROES and the client
acknowledging with NBD_FLAG_C_NO_ZEROES (only possible in
newstyle, whether or not it is fixed newstyle).  It doesn't
shave much off the wire, but we might as well implement it.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlex Bligh <alex@alex.org.uk>
Message-Id: <1476469998-28592-13-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since we know that the maximum name we are willing to accept
is small enough to stack-allocate, rework the iteration over
NBD_OPT_LIST responses to reuse a stack buffer rather than
allocating every time.  Furthermore, we don't even have to
allocate if we know the server's length doesn't match what
we are searching for.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-12-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The server has a nice helper function nbd_negotiate_drop_sync()
which lets it easily ignore fluff from the client (such as the
payload to an unknown option request).  We can't quite make it
common, since it depends on nbd_negotiate_read() which handles
coroutine magic, but we can copy the idea into the client where
we have places where we want to ignore data (such as the
description tacked on the end of NBD_REP_SERVER).
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-11-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The NBD spec says that a client should send NBD_OPT_ABORT
rather than just dropping the connection, if the client doesn't
like something the server sent during option negotiation.  This
is a best-effort attempt only, and can only be done in places
where we know the server is still in sync with what we've sent,
whether or not we've read everything the server has sent.
Technically, the server then has to reply with NBD_REP_ACK, but
it's not worth complicating the client to wait around for that
reply.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-10-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Rather than open-coding each option request, it's easier to
have common helper functions do the work.  That in turn requires
having convenient packed types for handling option requests
and replies.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-9-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The NBD Protocol allows us to send human-readable messages
along with any NBD_REP_ERR error during option negotiation;
make use of this fact for clients that know what to do with
our message.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-8-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Rather than open-coding NBD_REP_SERVER, reuse the code we
already have by adding a length parameter.  Additionally,
the refactoring will make adding NBD_OPT_GO in a later patch
easier.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-7-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Our coding convention prefers CamelCase names, and we already
have other existing structs with NBDFoo naming.  Let's be
consistent, before later patches add even more structs.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-6-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

It's better to use consistent capitalization of the namespace
used for NBD functions; we have more instances of NBD* than
Nbd*.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-5-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

We have both 'struct NBDRequest' and 'struct nbd_request'; making
it confusing to see which does what.  Furthermore, we want to
rename nbd_request to align with our normal CamelCase naming
conventions.  So, rename the struct which is used to associate
the data received during request callbacks, while leaving the
shorter name for the description of the request sent over the
wire in the NBD protocol.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-4-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Current upstream NBD documents that requests have a 16-bit flags,
followed by a 16-bit type integer; although older versions mentioned
only a 32-bit field with masking to find flags.  Since the protocol
is in network order (big-endian over the wire), the ABI is unchanged;
but dealing with the flags as a separate field rather than masking
will make it easier to add support for upcoming NBD extensions that
increase the number of both flags and commands.

Improve some comments in nbd.h based on the current upstream
NBD protocol (https://github.com/yoe/nbd/blob/master/doc/proto.md),
and touch some nearby code to keep checkpatch.pl happy.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-3-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The NBD protocol allows servers to advertise a human-readable
description alongside an export name during NBD_OPT_LIST.  Add
an option to pass through the user's string to the NBD client.

Doing this also makes it easier to test commit 200650d4, which
is the client counterpart of receiving the description.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-2-git-send-email-eblake@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

If the memory backend file is not large enough to hold the required 'size',
Qemu will report error and exit.
Signed-off-by: NHaozhong Zhang <haozhong.zhang@intel.com>
Message-Id: <20161027042300.5929-3-haozhong.zhang@intel.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>
Message-Id: <20161102010551.2723-1-haozhong.zhang@intel.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Commit 35c5a52d "acpi: do not use TARGET_PAGE_SIZE" changed struct
NvdimmDsmIn from a variable-size structure to a fixed-size structure of
4096 bytes. It forgot to adjust an assert in
nvdimm_dsm_set_label_data(..., NvdimmDsmIn *in, ...):
    assert(sizeof(*in) + sizeof(*set_label_data) + set_label_data->length <=
           4096);
which could crash QEMU when guest writes NVDIMM labels.

Fix it by replacing sizeof(*in) by offsetof(NvdimmDsmIn, arg3).
Signed-off-by: NHaozhong Zhang <haozhong.zhang@intel.com>
Reported-by: NDan Williams <dan.j.williams@intel.com>
Tested-by: NDan Williams <dan.j.williams@intel.com>
Reviewed-by: NXiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

The initialization was missed before, resulting in some
bad data in the smbus case.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

I misunderstood the workings of the power settings, the power off
is a force off operation and there needs to be a separate graceful
shutdown operation.  So replace the force off operation with a
graceful shutdown.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

The original commit:

  commit 67aa56fc
  Author: Corey Minyard <cminyard@mvista.com>
  Date:   Thu Dec 17 12:50:06 2015 -0600

    ipmi: Add an external connection simulation interface

defined a new variable CONFIG_IPMI_EXTERN, but then went
on to mistakely use the pre-existing CONFIG_IPMI_LOCAL
variable.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

This is allowed by the IPMI specification for graceful shutdown,
so implement it.
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

When issuing a chassis 'powerdown' control command, the routine
qemu_system_shutdown_request() should be used to exit the guest.
qemu_system_powerdown_request() will initiate a soft shutdown which is
not what is required by the IPMI (28.3 Chassis Control Command):

    0h = power down. Force system into soft off (S4/S45) state. This
    is for 'emergency' management power down actions. The command does
    not initiate a clean shut-down of the operating system prior to
    powering down the system
Signed-off-by: NCédric Le Goater <clg@kaod.org>
Signed-off-by: NCorey Minyard <cminyard@mvista.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Get rid of the unnecessary mutex, it was a vestige
of something else that was not done.  That way we don't
have to free it.
Signed-off-by: NCorey Minyard <cminyard@mvista.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>

No hotplug support, make sure it doesn't happen.
Signed-off-by: NCorey Minyard <cminyard@mvista.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>

_GPE.E04 is dedicated for nvdimm device hotplug
Signed-off-by: NXiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

_FIT is required for hotplug support, guest will inquire the updated
device info from it if a hotplug event is received

As FIT buffer is not completely mapped into guest address space, so a
new function, Read FIT whose UUID is UUID
648B9CF2-CDA1-4312-8AD9-49C4AF32BD62, handle 0x10000, function index
is 0x1, is reserved by QEMU to read the piece of FIT buffer. The buffer
is concatenated before _FIT return

Refer to docs/specs/acpi-nvdimm.txt for detailed design
Signed-off-by: NXiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

The buffer is used to save the FIT info for all the presented nvdimm
devices which is updated after the nvdimm device is plugged or
unplugged. In the later patch, it will be used to construct NVDIMM
ACPI _FIT method which reflects the presented nvdimm devices after
nvdimm hotplug

As FIT buffer can not completely mapped into guest address space,
OSPM will exit to QEMU multiple times, however, there is the race
condition - FIT may be changed during these multiple exits, so that
some rules are introduced:
1) the user should hold the @lock to access the buffer and
2) mark @dirty whenever the buffer is updated.

@dirty is cleared for the first time OSPM gets fit buffer, if
dirty is detected in the later access, OSPM will restart the
access

As fit should be updated after nvdimm device is successfully realized
so that a new hotplug callback, post_hotplug, is introduced
Signed-off-by: NXiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>