On 10/20/2023 5:45 AM, Juan Quintela wrote:
> Steve Sistare <steven.sist...@oracle.com> wrote:
>> Add the cpr-reboot migration mode. Usage:
>>
>> $ qemu-system-$arch -monitor stdio ...
>> QEMU 8.1.50 monitor - type 'help' for more information
>> (qemu) migrate_set_capability x-ignore-shared on
>> (qemu) migrate_set_parameter mode cpr-reboot
>> (qemu) migrate -d file:vm.state
>> (qemu) info status
>> VM status: paused (postmigrate)
>> (qemu) quit
>>
>> $ qemu-system-$arch -monitor stdio -incoming defer ...
>> QEMU 8.1.50 monitor - type 'help' for more information
>> (qemu) migrate_set_capability x-ignore-shared on
>> (qemu) migrate_set_parameter mode cpr-reboot
>> (qemu) migrate_incoming file:vm.state
>> (qemu) info status
>> VM status: running
>>
>> In this mode, the migrate command saves state to a file, allowing one
>> to quit qemu, reboot to an updated kernel, and restart an updated version
>> of qemu. The caller must specify a migration URI that writes to and reads
>> from a file. Unlike normal mode, the use of certain local storage options
>> does not block the migration, but the caller must not modify guest block
>> devices between the quit and restart. The guest RAM memory-backend must
>> be shared, and the @x-ignore-shared migration capability must be set,
>> to avoid saving RAM to the file. Guest RAM must be non-volatile across
>> reboot, such as by backing it with a dax device, but this is not enforced.
>> The restarted qemu arguments must match those used to initially start qemu,
>> plus the -incoming option.
>
> Please, add this message to doc/<somewhere> instead (or additionally) to
> the commit log.
>
>> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
>> ---
>> qapi/migration.json | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/qapi/migration.json b/qapi/migration.json
>> index 184fb78..2d862fa 100644
>> --- a/qapi/migration.json
>> +++ b/qapi/migration.json
>> @@ -620,9 +620,23 @@
>> #
>> # @normal: the original form of migration. (since 8.2)
>> #
>> +# @cpr-reboot: The migrate command saves state to a file, allowing one to
>> +# quit qemu, reboot to an updated kernel, and restart an
>> updated
>> +# version of qemu. The caller must specify a migration URI
>> +# that writes to and reads from a file. Unlike normal mode,
>> +# the use of certain local storage options does not block the
>> +# migration, but the caller must not modify guest block devices
>> +# between the quit and restart. The guest RAM memory-backend
>> +# must be shared, and the @x-ignore-shared migration capability
>> +# must be set, to avoid saving it to the file. Guest RAM must
>> +# be non-volatile across reboot, such as by backing it with
>> +# a dax device, but this is not enforced. The restarted qemu
>> +# arguments must match those used to initially start qemu, plus
>> +# the -incoming option. (since 8.2)
>> +#
>> ##
>> { 'enum': 'MigMode',
>> - 'data': [ 'normal' ] }
>> + 'data': [ 'normal', 'cpr-reboot' ] }
>>
>> ##
>> # @BitmapMigrationBitmapAliasTransform:
>
> It only works with file backend, and we don't have any check for that.
> Wondering how to add that check.
Actually, it works for other backends, but the ram contents are saved in the
state file, which is slower. I should spell that out in the json comment and
in the commit message.
> Additionally, you are not adding a migration test that does exactly what
> you put there in the comment.
I provide tests/avocado/cpr.py in the original long series. Would you
like me to add it to this series, or post it later? Would you prefer I
add a test to tests/qtest/migration-test.c?
- Steve
