481 Commits

Author SHA1 Message Date
Fabiano Rosas
f523e5aa5f migration: Move CPR HUP watch to cpr-transfer.c
Move this CPR-specific code into a cpr file. While here, give the
functions more significant names.

This makes the new idea (after cpr-transfer) of having two parts to
qmp_migrate slightly more obvious: either wait for the hangup or
continue directly.

Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Prasad Pandit <pjp@fedoraproject.org>
Link: https://lore.kernel.org/qemu-devel/20260123141656.6765-24-farosas@suse.de
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2026-01-23 11:32:19 -03:00
Zhao Liu
bb9f99e9ba i386/machine: Use VMSTATE_UINTTL_SUB_ARRAY for vmstate of CPUX86State.regs
Before expanding the number of elements in the CPUX86State.regs array,
first use VMSTATE_UINTTL_SUB_ARRAY for the regs' vmstate to avoid the
type_check_array failure.

VMSTATE_UINTTL_SUB_ARRAY will also be used for subsequently added elements
in regs array.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20251211070942.3612547-3-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-12-27 10:11:11 +01:00
Paolo Bonzini
9f6b0553eb include: move hw/vmstate-if.h to hw/core/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2025-12-27 10:11:08 +01:00
Philippe Mathieu-Daudé
0d42e48c73 Revert "migration/vmstate: remove VMSTATE_BUFFER_POINTER_UNSAFE macro"
Next commit will re-use VMSTATE_BUFFER_POINTER_UNSAFE().

This reverts commit 58341158d0.

Suggested-by: Fiona Ebner <f.ebner@proxmox.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
2025-12-09 21:00:15 +01:00
Vladimir Sementsov-Ogievskiy
8c3843638c migration: vmsd errp handlers: return bool
No code actually depend on specific errno values returned by
vmstate_load_state. The only use of it is to check for success,
and sometimes inject numeric error values into error messages
in migration code. The latter is not a stopper for gradual
conversion to "errp + bool return value" APIs.

Big analysis of vmstate_load_state() callers, showing that
specific errno values are not actually used, is done by Peter
here:

https://lore.kernel.org/qemu-devel/aQDdRn8t0B8oE3gf@x1.local/

Converting of vmstate_load_state() itself will follow in
another series.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Link: https://lore.kernel.org/r/20251028170926.77219-2-vsementsov@yandex-team.ru
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-11-03 16:04:10 -05:00
Markus Armbruster
3ca0a0ab05 migration: Use bitset of MigMode instead of variable arguments
migrate_add_blocker_modes() and migration_add_notifier_modes use
variable arguments for a set of migration modes.  The variable
arguments get collected into a bitset for processsing.  Take a bitset
argument instead, it's simpler.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20251027064503.1074255-3-armbru@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-11-03 16:04:10 -05:00
Peter Xu
6a65fdee8a migration/cpr: Fix coverity report in cpr_exec_persist_state()
Per reported and analyzed by Peter:

https://lore.kernel.org/r/CAFEAcA_mUQ2NeoguR5efrhw7XYGofnriWEA=+Dg+Ocvyam1wAw@mail.gmail.com

mfd leak is a false positive, try to use a coverity annotation (which I
didn't find manual myself, but still give it a shot).

Fix the other one by capture error if setenv() failed.  When at it, pass
the error to the top (cpr_state_save()).  Along the way, changing all
retval to bool when errp is around.

Resolves: Coverity CID 1641391
Resolves: Coverity CID 1641392
Fixes: efc6587313 ("migration: cpr-exec save and load")
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20251021220407.2662288-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-11-03 16:04:09 -05:00
Philippe Mathieu-Daudé
346479c304 migration: Remove unused VMSTATE_UINTTL_EQUAL[_V]() macros
The last use of VMSTATE_UINTTL_EQUAL() was removed in commit
16a2497bd4 ("target-ppc: Fix CPU migration from qemu-2.6 <->
later versions"), 9 years ago; remove it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/20251016160313.25751-1-philmd@linaro.org
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-11-03 16:04:09 -05:00
Michael Tokarev
58341158d0 migration/vmstate: remove VMSTATE_BUFFER_POINTER_UNSAFE macro
The only user of this macro was VirtIONet.vlans, which has been
converted to regular VMSTATE_BUFFER.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Peter Xu <peterx@redhat.com>
Message-ID: <20251023135316.31128-3-mjt@tls.msk.ru>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
2025-10-28 08:08:11 +01:00
Richard Henderson
bd6aa0d1e5 Merge tag 'staging-pull-request' of https://gitlab.com/peterx/qemu into staging
Migration/Memory Pull for 10.2

- PeterX's fix on tls warning for preempt channel when migratino completes
- Arun's series to enhance error reporting for vTPM and migration framework
- PeterX's patch to cleanup multifd send TLS BYE messages
- Juraj's fix on postcopy start state transition when switchover failed
- Yanfei's fix to migrate APIC before VFIO-PCI to avoid irq fallbacks
- Dan's cleanup to simplify error reporting in qemu_fill_buffer()
- PeterM's fix on address space leak when cpu hot plug / unplug
- Steve's cpr-exec wholeset

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# gpg: Signature made Fri 03 Oct 2025 08:39:14 AM PDT
# gpg:                using EDDSA key B9184DC20CC457DACF7DD1A93B5FCCCDF3ABD706
# gpg:                issuer "peterx@redhat.com"
# gpg: Good signature from "Peter Xu <xzpeter@gmail.com>" [unknown]
# gpg:                 aka "Peter Xu <peterx@redhat.com>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: B918 4DC2 0CC4 57DA CF7D  D1A9 3B5F CCCD F3AB D706

* tag 'staging-pull-request' of https://gitlab.com/peterx/qemu: (45 commits)
  migration-test: test cpr-exec
  vfio: cpr-exec mode
  migration: cpr-exec docs
  migration: cpr-exec mode
  migration: cpr-exec save and load
  migration: cpr-exec-command parameter
  oslib: qemu_clear_cloexec
  migration: add cpr_walk_fd
  migration: multi-mode notifier
  migration: simplify error reporting after channel read
  physmem: Destroy all CPU AddressSpaces on unrealize
  memory: New AS helper to serialize destroy+free
  include/system/memory.h: Clarify address_space_destroy() behaviour
  migration: ensure APIC is loaded prior to VFIO PCI devices
  migration: Fix state transition in postcopy_start() error handling
  migration/multifd/tls: Cleanup BYE message processing on sender side
  migration: HMP: Adjust the order of output fields
  migration: Make migration_has_failed() work even for CANCELLING
  io/crypto: Move tls premature termination handling into QIO layer
  backends/tpm: Propagate vTPM error on migration failure
  ...

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2025-10-04 09:10:58 -07:00
Steve Sistare
a3eae205c6 migration: cpr-exec mode
Add the cpr-exec migration mode.  Usage:
  qemu-system-$arch -machine aux-ram-share=on ...
  migrate_set_parameter mode cpr-exec
  migrate_set_parameter cpr-exec-command \
    <arg1> <arg2> ... -incoming <uri-1> \
  migrate -d <uri-1>

The migrate command stops the VM, saves state to uri-1,
directly exec's a new version of QEMU on the same host,
replacing the original process while retaining its PID, and
loads state from uri-1.  Guest RAM is preserved in place,
albeit with new virtual addresses.

The new QEMU process is started by exec'ing the command
specified by the @cpr-exec-command parameter.  The first word of
the command is the binary, and the remaining words are its
arguments.  The command may be a direct invocation of new QEMU,
or may be a non-QEMU command that exec's the new QEMU binary.

This mode creates a second migration channel that is not visible
to the user.  At the start of migration, old QEMU saves CPR state
to the second channel, and at the end of migration, it tells the
main loop to call cpr_exec.  New QEMU loads CPR state early, before
objects are created.

Because old QEMU terminates when new QEMU starts, one cannot
stream data between the two, so uri-1 must be a type,
such as a file, that accepts all data before old QEMU exits.
Otherwise, old QEMU may quietly block writing to the channel.

Memory-backend objects must have the share=on attribute, but
memory-backend-epc is not supported.  The VM must be started with
the '-machine aux-ram-share=on' option, which allows anonymous
memory to be transferred in place to the new process.  The memfds
are kept open across exec by clearing the close-on-exec flag, their
values are saved in CPR state, and they are mmap'd in new QEMU.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/1759332851-370353-7-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Steve Sistare
efc6587313 migration: cpr-exec save and load
To preserve CPR state across exec, create a QEMUFile based on a memfd, and
keep the memfd open across exec.  Save the value of the memfd in an
environment variable so post-exec QEMU can find it.

These new functions are called in a subsequent patch.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Link: https://lore.kernel.org/r/1759332851-370353-6-git-send-email-steven.sistare@oracle.com
[peterx: fix build for Windows]
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Steve Sistare
a9f9eee58b migration: add cpr_walk_fd
Add a helper to walk all CPR fd's and run a callback for each.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1759332851-370353-3-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Steve Sistare
dc79c7d5e1 migration: multi-mode notifier
Allow a notifier to be added for multiple migration modes.
To allow a notifier to appear on multiple per-node lists, use
a generic list type.  We can no longer use NotifierWithReturnList,
because it shoe horns the notifier onto a single list.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/1759332851-370353-2-git-send-email-steven.sistare@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Yanfei Xu
d943cef760 migration: ensure APIC is loaded prior to VFIO PCI devices
The load procedure of VFIO PCI devices involves setting up IRT
for each VFIO PCI devices. This requires determining whether an
interrupt is single-destination interrupt to decide between
Posted Interrupt(PI) or remapping mode for the IRTE. However,
determining this may require accessing the VM's APIC registers.

For example:
ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irqs)
  ...
    kvm_arch_irq_bypass_add_producer
      kvm_x86_call(pi_update_irte)
        vmx_pi_update_irte
          kvm_intr_is_single_vcpu

If the LAPIC has not been loaded yet, interrupts will use remapping
mode. To prevent the fallback of interrupt mode, keep APIC is always
loaded prior to VFIO PCI devices.

Signed-off-by: Yicong Shen <shenyicong.1023@bytedance.com>
Signed-off-by: Yanfei Xu <yanfei.xu@bytedance.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20250818131127.1021648-1-yanfei.xu@bytedance.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Arun Menon
40de712a89 migration: Add error-parameterized function variants in VMSD struct
- We need to have good error reporting in the callbacks in
  VMStateDescription struct. Specifically pre_save, pre_load
  and post_load callbacks.
- It is not possible to change these functions everywhere in one
  patch, therefore, we introduce a duplicate set of callbacks
  with Error object passed to them.
- So, in this commit, we implement 'errp' variants of these callbacks,
  introducing an explicit Error object parameter.
- This is a functional step towards transitioning the entire codebase
  to the new error-parameterized functions.
- Deliberately called in mutual exclusion from their counterparts,
  to prevent conflicts during the transition.
- New impls should preferentally use 'errp' variants of
  these methods, and existing impls incrementally converted.
  The variants without 'errp' are intended to be removed
  once all usage is converted.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-26-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Arun Menon
6f9fc6f501 migration: Remove error variant of vmstate_save_state() function
This commit removes the redundant vmstate_save_state_with_err()
function.

Previously, commit 969298f9d7 introduced vmstate_save_state_with_err()
to handle error propagation, while vmstate_save_state() existed for
non-error scenarios.
This is because there were code paths where vmstate_save_state_v()
(called internally by vmstate_save_state) did not explicitly set
errors on failure.

This change unifies error handling by
 - updating vmstate_save_state() to accept an Error **errp argument.
 - vmstate_save_state_v() ensures errors are set directly within the errp
   object, eliminating the need for two separate functions.

All calls to vmstate_save_state_with_err() are replaced with
vmstate_save_state(). This simplifies the API and improves code
maintainability.

vmstate_save_state() that only calls vmstate_save_state_v(),
by inference, also has errors set in errp in case of failure.
The errors are reported using error_report_err().
If we want the function to exit on error, then &error_fatal is
passed.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-24-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Arun Menon
d865e4aabd migration: push Error **errp into loadvm_process_enable_colo()
This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.
It is ensured that loadvm_process_enable_colo() must report an error
in errp, in case of failure.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-21-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:02 -04:00
Arun Menon
c632ffbd74 migration: push Error **errp into vmstate_load_state()
This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.
It is ensured that vmstate_load_state() must report an error
in errp, in case of failure.

The errors are temporarily reported using error_report_err().
This is removed in the subsequent patches in this series,
when we are actually able to propagate the error to the calling
function using errp. Whereas, if we want the function to exit on
error, then error_fatal is passed.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-2-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2025-10-03 09:48:01 -04:00
TANG Tiancheng
30478e2ff7 migration: Add support for a variable-length array of UINT32 pointers
Add support for defining a vmstate field which is a variable-length array
of pointers, and use this to define a VMSTATE_TIMER_PTR_VARRAY() which allows
a variable-length array of QEMUTimer* to be used by devices.

Message-id: 20250909-timers-v1-0-7ee18a9d8f4b@linux.alibaba.com
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: TANG Tiancheng <lyndra@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250911-timers-v3-2-60508f640050@linux.alibaba.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
2025-10-03 13:15:14 +10:00
Juraj Marcin
beeac2df5f migration: Rename save_live_complete_precopy_thread to save_complete_precopy_thread
Recent patch [1] renames the save_live_complete_precopy handler to
save_complete, as the machine is not live in most cases when this
handler is executed. The same is true also for
save_live_complete_precopy_thread, therefore this patch removes the
"live" keyword from the handler itself and related types to keep the
naming unified.

In contrast to save_complete, this handler is only executed at the end
of precopy, therefore the "precopy" keyword is retained.

[1]: https://lore.kernel.org/all/20250613140801.474264-7-peterx@redhat.com/

Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
Link: https://lore.kernel.org/r/20250626085235.294690-1-jmarcin@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-07-11 10:37:39 -03:00
Peter Xu
57c43e52bd migration: Rename save_live_complete_precopy to save_complete
Now after merging the precopy and postcopy version of complete() hook,
rename the precopy version from save_live_complete_precopy() to
save_complete().

Dropping the "live" when at it, because it's in most cases not live when
happening (in precopy).

No functional change intended.

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613140801.474264-7-peterx@redhat.com
[peterx: squash the fixup that covers a few more doc spots, per Juraj]
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-07-11 10:37:36 -03:00
Peter Xu
d7530a9682 migration: Drop save_live_complete_postcopy hook
The hook is only defined in two vmstate users ("ram" and "block dirty
bitmap"), meanwhile both of them define the hook exactly the same as the
precopy version.  Hence, this postcopy version isn't needed.

No functional change intended.

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613140801.474264-6-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-07-11 10:37:35 -03:00
Steve Sistare
a6f2f9c42f migration: vfio cpr state hook
Define a list of vfio devices in CPR state, in a subsection so that
older QEMU can be live updated to this version.  However, new QEMU
will not be live updateable to old QEMU.  This is acceptable because
CPR is not yet commonly used, and updates to older versions are unusual.

The contents of each device object will be defined by the vfio subsystem
in a subsequent patch.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-14-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-07-03 13:42:28 +02:00
Steve Sistare
ccfc6715cf migration: cpr_get_fd_param helper
Add the helper function cpr_get_fd_param, to use when preserving
a file descriptor that is opened externally and passed to QEMU.
cpr_get_fd_param returns a descriptor number either from a QEMU
command-line parameter, from a getfd command, or from CPR state.

When a descriptor is passed to new QEMU via SCM_RIGHTS, its number
changes.  Hence, during CPR, the command-line parameter is ignored
in new QEMU, and over-ridden by the value found in CPR state.

Similarly, if the descriptor was originally specified by a getfd
command in old QEMU, the fd number is not known outside of QEMU,
and it changes when sent to new QEMU via SCM_RIGHTS.  Hence the
user cannot send getfd to new QEMU, but when the user sends a
hotplug command that references the fd, cpr_get_fd_param finds
its value in CPR state.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/qemu-devel/1751493538-202042-5-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-07-03 13:42:28 +02:00
Steve Sistare
081c09dc52 migration: lower handler priority
Define a vmstate priority that is lower than the default, so its handlers
run after all default priority handlers.  Since 0 is no longer the default
priority, translate an uninitialized priority of 0 to MIG_PRI_DEFAULT.

CPR for vfio will use this to install handlers for containers that run
after handlers for the devices that they contain.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1749569991-25171-3-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-06-11 14:01:58 +02:00
Steve Sistare
f95fd60ac1 migration: cpr helpers
Add the cpr_incoming_needed, cpr_open_fd, and cpr_resave_fd helpers,
for use when adding cpr support for vfio and iommufd.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/1749569991-25171-2-git-send-email-steven.sistare@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-06-11 14:01:58 +02:00
Peter Xu
1d48111601 migration: Add save_postcopy_prepare() savevm handler
Add a savevm handler for a module to opt-in sending extra sections right
before postcopy starts, and before VM is stopped.

RAM will start to use this new savevm handler in the next patch to do flush
and sync for multifd pages.

Note that we choose to do it before VM stopped because the current only
potential user is not sensitive to VM status, so doing it before VM is
stopped is preferred to enlarge any postcopy downtime.

It is still a bit unfortunate that we need to introduce such a new savevm
handler just for the only use case, however it's so far the cleanest.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <20250411114534.3370816-4-ppandit@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-05-02 11:09:36 -04:00
Steve Sistare
1632a2017f migration: cpr_is_incoming
Define the cpr_is_incoming helper, to be used in several cpr fix patches.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-ID: <1741380954-341079-2-git-send-email-steven.sistare@oracle.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-03-14 09:29:19 -03:00
Maciej S. Szmigiero
8305921a91 migration: Add save_live_complete_precopy_thread handler
This SaveVMHandler helps device provide its own asynchronous transmission
of the remaining data at the end of a precopy phase via multifd channels,
in parallel with the transfer done by save_live_complete_precopy handlers.

These threads are launched only when multifd device state transfer is
supported.

Management of these threads in done in the multifd migration code,
wrapping them in the generic thread pool.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/qemu-devel/eac74a4ca7edd8968bbf72aa07b9041c76364a16.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
a1131aa942 migration/multifd: Add multifd_device_state_supported()
Since device state transfer via multifd channels requires multifd
channels with packets and is currently not compatible with multifd
compression add an appropriate query function so device can learn
whether it can actually make use of it.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/1ff0d98b85f470e5a33687406e877583b8fab74e.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
0525b91a0b migration/multifd: Device state transfer support - send side
A new function multifd_queue_device_state() is provided for device to queue
its state for transmission via a multifd channel.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/ebd55768d3e5fecb5eb3f197bad9c0c07e5bc084.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
b1937fd1eb migration: Add thread pool of optional load threads
Some drivers might want to make use of auxiliary helper threads during VM
state loading, for example to make sure that their blocking (sync) I/O
operations don't block the rest of the migration process.

Add a migration core managed thread pool to facilitate this use case.

The migration core will wait for these threads to finish before
(re)starting the VM at destination.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/b09fd70369b6159c75847e69f235cb908b02570c.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
a30363db08 migration: Add qemu_loadvm_load_state_buffer() and its handler
qemu_loadvm_load_state_buffer() and its load_state_buffer
SaveVMHandler allow providing device state buffer to explicitly
specified device via its idstr and instance id.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/71ca753286b87831ced4afd422e2e2bed071af25.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
4e55cb3cde migration: Add MIG_CMD_SWITCHOVER_START and its load handler
This QEMU_VM_COMMAND sub-command and its switchover_start SaveVMHandler is
used to mark the switchover point in main migration stream.

It can be used to inform the destination that all pre-switchover main
migration stream data has been sent/received so it can start to process
post-switchover data that it might have received via other migration
channels like the multifd ones.

Add also the relevant MigrationState bit stream compatibility property and
its hw_compat entry.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Zhang Chen <zhangckid@gmail.com> # for the COLO part
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/311be6da85fc7e49a7598684d80aa631778dcbce.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Maciej S. Szmigiero
d3237d0d85 migration: Clarify that {load, save}_cleanup handlers can run without setup
It's possible for {load,save}_cleanup SaveVMHandlers to get called without
the corresponding {load,save}_setup handler being called first.

One such example is if {load,save}_setup handler of a proceeding device
returns error.
In this case the migration core cleanup code will call all corresponding
cleanup handlers, even for these devices which haven't had its setup
handler called.

Since this behavior can generate some surprises let's clearly document it
in these SaveVMHandlers description.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Link: https://lore.kernel.org/qemu-devel/991636623fb780350f493b5f045cb17e13ce4c0f.1741124640.git.maciej.szmigiero@oracle.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2025-03-06 06:47:33 +01:00
Steve Sistare
624e6e654e migration: cpr-transfer mode
Add the cpr-transfer migration mode, which allows the user to transfer
a guest to a new QEMU instance on the same host with minimal guest pause
time, by preserving guest RAM in place, albeit with new virtual addresses
in new QEMU, and by preserving device file descriptors.  Pages that were
locked in memory for DMA in old QEMU remain locked in new QEMU, because the
descriptor of the device that locked them remains open.

cpr-transfer preserves memory and devices descriptors by sending them to
new QEMU over a unix domain socket using SCM_RIGHTS.  Such CPR state cannot
be sent over the normal migration channel, because devices and backends
are created prior to reading the channel, so this mode sends CPR state
over a second "cpr" migration channel.  New QEMU reads the cpr channel
prior to creating devices or backends.  The user specifies the cpr channel
in the channel arguments on the outgoing side, and in a second -incoming
command-line parameter on the incoming side.

The user must start old QEMU with the the '-machine aux-ram-share=on' option,
which allows anonymous memory to be transferred in place to the new process
by transferring a memory descriptor for each ram block.  Memory-backend
objects must have the share=on attribute, but memory-backend-epc is not
supported.

The user starts new QEMU on the same host as old QEMU, with command-line
arguments to create the same machine, plus the -incoming option for the
main migration channel, like normal live migration.  In addition, the user
adds a second -incoming option with channel type "cpr".  This CPR channel
must support file descriptor transfer with SCM_RIGHTS, i.e. it must be a
UNIX domain socket.

To initiate CPR, the user issues a migrate command to old QEMU, adding
a second migration channel of type "cpr" in the channels argument.
Old QEMU stops the VM, saves state to the migration channels, and enters
the postmigrate state.  New QEMU mmap's memory descriptors, and execution
resumes.

The implementation splits qmp_migrate into start and finish functions.
Start sends CPR state to new QEMU, which responds by closing the CPR
channel.  Old QEMU detects the HUP then calls finish, which connects the
main migration channel.

In summary, the usage is:

  qemu-system-$arch -machine aux-ram-share=on ...

  start new QEMU with "-incoming <main-uri> -incoming <cpr-channel>"

  Issue commands to old QEMU:
    migrate_set_parameter mode cpr-transfer

    {"execute": "migrate", ...
        {"channel-type": "main"...}, {"channel-type": "cpr"...} ... }

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-17-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-29 11:56:24 -03:00
Steve Sistare
b3698869f4 migration: cpr-transfer save and load
Add functions to create a QEMUFile based on a unix URI, for saving or
loading, for use by cpr-transfer mode to preserve CPR state.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-16-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-29 11:43:05 -03:00
Steve Sistare
e3965dc352 migration: VMSTATE_FD
Define VMSTATE_FD for declaring a file descriptor field in a
VMStateDescription.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-15-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-29 11:43:05 -03:00
Steve Sistare
f2374f0fc3 migration: enhance migrate_uri_parse
Export migrate_uri_parse for use outside migration internals, and define
a method migrate_is_uri that indicates when migrate_uri_parse should
be used.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-12-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-29 11:43:04 -03:00
Steve Sistare
e7d79011a4 migration: cpr-state
CPR must save state that is needed after QEMU is restarted, when devices
are realized.  Thus the extra state cannot be saved in the migration
channel, as objects must already exist before that channel can be loaded.
Instead, define auxilliary state structures and vmstate descriptions, not
associated with any registered object, and serialize the aux state to a
cpr-specific channel in cpr_state_save.  Deserialize in cpr_state_load
after QEMU restarts, before devices are realized.

Provide accessors for clients to register file descriptors for saving.
The mechanism for passing the fd's to the new process will be specific
to each migration mode, and added in subsequent patches.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-8-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-29 11:43:04 -03:00
Peter Xu
8597af7615 migration/block: Rewrite disk activation
This patch proposes a flag to maintain disk activation status globally.  It
mostly rewrites disk activation mgmt for QEMU, including COLO and QMP
command xen_save_devices_state.

Backgrounds
===========

We have two problems on disk activations, one resolved, one not.

Problem 1: disk activation recover (for switchover interruptions)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When migration is either cancelled or failed during switchover, especially
when after the disks are inactivated, QEMU needs to remember re-activate
the disks again before vm starts.

It used to be done separately in two paths: one in qmp_migrate_cancel(),
the other one in the failure path of migration_completion().

It used to be fixed in different commits, all over the places in QEMU.  So
these are the relevant changes I saw, I'm not sure if it's complete list:

 - In 2016, commit fe904ea824 ("migration: regain control of images when
   migration fails to complete")

 - In 2017, commit 1d2acc3162 ("migration: re-active images while migration
   been canceled after inactive them")

 - In 2023, commit 6dab4c93ec ("migration: Attempt disk reactivation in
   more failure scenarios")

Now since we have a slightly better picture maybe we can unify the
reactivation in a single path.

One side benefit of doing so is, we can move the disk operation outside QMP
command "migrate_cancel".  It's possible that in the future we may want to
make "migrate_cancel" be OOB-compatible, while that requires the command
doesn't need BQL in the first place.  This will already do that and make
migrate_cancel command lightweight.

Problem 2: disk invalidation on top of invalidated disks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is an unresolved bug for current QEMU.  Link in "Resolves:" at the
end.  It turns out besides the src switchover phase (problem 1 above), QEMU
also needs to remember block activation on destination.

Consider two continuous migration in a row, where the VM was always paused.
In that scenario, the disks are not activated even until migration
completed in the 1st round.  When the 2nd round starts, if QEMU doesn't
know the status of the disks, it needs to try inactivate the disk again.

Here the issue is the block layer API bdrv_inactivate_all() will crash a
QEMU if invoked on already inactive disks for the 2nd migration.  For
detail, see the bug link at the end.

Implementation
==============

This patch proposes to maintain disk activation with a global flag, so we
know:

  - If we used to inactivate disks for migration, but migration got
  cancelled, or failed, QEMU will know it should reactivate the disks.

  - On incoming side, if the disks are never activated but then another
  migration is triggered, QEMU should be able to tell that inactivate is
  not needed for the 2nd migration.

We used to have disk_inactive, but it only solves the 1st issue, not the
2nd.  Also, it's done in completely separate paths so it's extremely hard
to follow either how the flag changes, or the duration that the flag is
valid, and when we will reactivate the disks.

Convert the existing disk_inactive flag into that global flag (also invert
its naming), and maintain the disk activation status for the whole
lifecycle of qemu.  That includes the incoming QEMU.

Put both of the error cases of source migration (failure, cancelled)
together into migration_iteration_finish(), which will be invoked for
either of the scenario.  So from that part QEMU should behave the same as
before.  However with such global maintenance on disk activation status, we
not only cleanup quite a few temporary paths that we try to maintain the
disk activation status (e.g. in postcopy code), meanwhile it fixes the
crash for problem 2 in one shot.

For freshly started QEMU, the flag is initialized to TRUE showing that the
QEMU owns the disks by default.

For incoming migrated QEMU, the flag will be initialized to FALSE once and
for all showing that the dest QEMU doesn't own the disks until switchover.
That is guaranteed by the "once" variable.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2395
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Message-Id: <20241206230838.1111496-7-peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2025-01-09 17:38:57 -03:00
Avihai Horon
3bdb1a75f1 migration: Unexport migration_is_active()
After being removed from VFIO and dirty limit, migration_is_active() no
longer has any users outside the migration subsystem, and in fact, it's
only used in migration.c.

Unexport it and also relocate it so it can be made static.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20241218134022.21264-8-avihaih@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2024-12-26 07:23:38 +01:00
Avihai Horon
844ed0f762 migration: Drop migration_is_device()
After being removed from VFIO, migration_is_device() no longer has any
users. Drop it.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Tested-by: Joao Martins <joao.m.martins@oracle.com>
Link: https://lore.kernel.org/r/20241218134022.21264-7-avihaih@nvidia.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2024-12-26 07:23:38 +01:00
Peter Xu
34a8892dec migration: Drop migration_is_idle()
Now with the current migration_is_running(), it will report exactly the
opposite of what will be reported by migration_is_idle().

Drop migration_is_idle(), instead use "!migration_is_running()" which
should be identical on functionality.

In reality, most of the idle check is inverted, so it's even easier to
write with "migrate_is_running()" check.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-6-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-10-31 15:48:18 -04:00
Peter Xu
f018eb62b2 migration: Drop migration_is_setup_or_active()
This helper is mostly the same as migration_is_running(), except that one
has COLO reported as true, the other has CANCELLING reported as true.

Per my past years experience on the state changes, none of them should
matter.

To make it slightly safer, report both COLO || CANCELLING to be true in
migration_is_running(), then drop the other one.  We kept the 1st only
because the name is simpler, and clear enough.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-10-31 15:48:18 -04:00
Peter Xu
64dcd2c9c6 migration: Unexport ram_mig_init()
It's only used within migration/.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-10-31 15:48:18 -04:00
Peter Xu
a4ddab3581 migration: Unexport dirty_bitmap_mig_init()
It's only used within migration/, so it shouldn't be exported.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20241024213056.1395400-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
2024-10-31 15:48:18 -04:00
Philippe Mathieu-Daudé
04b09de16d migration: Remove unused VMSTATE_ARRAY_TEST() macro
Last use of VMSTATE_ARRAY_TEST() was removed in commit 46baa9007f
("migration/i386: Remove old non-softfloat 64bit FP support"), we
can safely get rid of it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
2024-06-21 14:37:58 -03:00
Richard Henderson
7e1c004701 Merge tag 'migration-20240522-pull-request' of https://gitlab.com/farosas/qemu into staging
Migration pull request

- Li Zhijian's COLO minor fixes
- Marc-André's virtio-gpu fix
- Fiona's virtio-net USO fix
- A couple of migration-test fixes from Thomas

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* tag 'migration-20240522-pull-request' of https://gitlab.com/farosas/qemu:
  tests/qtest/migration-test: Fix the check for a successful run of analyze-migration.py
  tests/qtest/migration-test: Run some basic tests on s390x and ppc64 with TCG, too
  hw/core/machine: move compatibility flags for VirtIO-net USO to machine 8.1
  virtio-gpu: fix v2 migration
  migration: fix a typo
  migration: add "exists" info to load-state-field trace
  migration/colo: Tidy up bql_unlock() around bdrv_activate_all()
  migration/colo: make colo_incoming_co() return void
  migration/colo: Minor fix for colo error message

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2024-05-22 15:32:25 -07:00