Re: [Qemu-devel] [PATCH v2 0/5] Add ignore-external migration capability

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Yury Kotov (yury-kotov@yandex-team.ru) wrote:
> Hi,
> 
> The series adds a migration capability, which allows to skip shared RAM blocks
> during the migration. It's useful for fast local migration. E.g. to update QEMU
> for the running guests.
> 
> Usage example:
> 1. Start source VM:
>    qemu-system-x86 \
>      -m 4G \
>      -object memory-backend-file,id=mem0,size=4G,share=on,mem-path=/dev/shm/mem0 \
>      -numa node,memdev=mem0 \
>      -qmp unix:/tmp/qemu-qmp-1.sock,server,nowait \
> 
> 2. Start target VM:
>    qemu-system-x86 \
>      -m 4G \
>      -object memory-backend-file,id=mem0,size=4G,share=on,mem-path=/dev/shm/mem0 \
>      -numa node,memdev=mem0 \
>      -qmp unix:/tmp/qemu-qmp-2.sock,server,nowait \
>      -incoming defer
> 
> 3. Enable ignore-external capability on both VMs:
>    { "execute": "migrate-set-capabilities" , "arguments":
>      { "capabilities": [ { "capability": "x-ignore-external", "state": true } ] } }
> 
> 4. Start migration.
> 
> Another use case I keep in mind is to migrate to file. Usage is very similar.

Hi,
  I've cc'd in Eric, Lai and Peter, all who were asking for something
similar last year;  can you all confirm this patch does what you need or
can work with what you needed to do?

Dave

> V1 to V2:
> * Keep migration stream compatibility
> * Reuse the existing code to ignore unwanted RAMBlocks
> * Add capability validation feature
> * ignore-external -> ignore-shared
> 
> Regards,
> Yury
> 
> Yury Kotov (5):
>   exec: Change RAMBlockIterFunc definition
>   migration: Move qemu_ram_foreach_migratable_block to migration code
>   migration: Introduce ignore-shared capability
>   tests/migration-test: Add a test for ignore-shared capability
>   migration: Add capabilities validation
> 
>  exec.c                    |  38 ++++++-------
>  include/exec/cpu-common.h |   7 +--
>  migration/migration.c     |   9 ++++
>  migration/migration.h     |  11 +++-
>  migration/postcopy-ram.c  |  48 +++++++++--------
>  migration/ram.c           |  86 ++++++++++++++++++++++++++----
>  migration/rdma.c          |   9 ++--
>  migration/savevm.c        | 101 +++++++++++++++++++++++++++++++++++
>  qapi/migration.json       |   5 +-
>  stubs/ram-block.c         |  15 ++++++
>  tests/migration-test.c    | 109 +++++++++++++++++++++++++++++++-------
>  util/vfio-helpers.c       |   6 +--
>  12 files changed, 361 insertions(+), 83 deletions(-)
> 
> -- 
> 2.20.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK