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Re: [Qemu-devel] [PATCH v2 for-2.11] migration, xen: Fix block image loc
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v2 for-2.11] migration, xen: Fix block image lock issue on live migration |
Date: |
Mon, 20 Nov 2017 14:52:48 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
* Anthony PERARD (address@hidden) wrote:
> When doing a live migration of a Xen guest with libxl, the images for
> block devices are locked by the original QEMU process, and this prevent
> the QEMU at the destination to take the lock and the migration fail.
>
> From QEMU point of view, once the RAM of a domain is migrated, there is
> two QMP commands, "stop" then "xen-save-devices-state", at which point a
> new QEMU is spawned at the destination.
>
> Release locks in "xen-save-devices-state" so the destination can takes
> them, if it's a live migration.
>
> This patch add the "live" parameter to "xen-save-devices-state" which
> default to true so older version of libxenlight can work with newer
> version of QEMU.
>
> Signed-off-by: Anthony PERARD <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> Changes in V2:
> - add the live parameter
>
> CC: Kevin Wolf <address@hidden>
>
> also CCing libxl maintainers:
> CC: Ian Jackson <address@hidden>
> CC: Wei Liu <address@hidden>
> ---
> migration/savevm.c | 23 ++++++++++++++++++++++-
> qapi/migration.json | 6 +++++-
> 2 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index 4a88228614..7bc4e23e65 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -2242,13 +2242,20 @@ int save_snapshot(const char *name, Error **errp)
> return ret;
> }
>
> -void qmp_xen_save_devices_state(const char *filename, Error **errp)
> +void qmp_xen_save_devices_state(const char *filename, bool has_live, bool
> live,
> + Error **errp)
> {
> QEMUFile *f;
> QIOChannelFile *ioc;
> int saved_vm_running;
> int ret;
>
> + if (!has_live) {
> + /* live default to true so old version of Xen tool stack can have a
> + * successfull live migration */
> + live = true;
> + }
> +
> saved_vm_running = runstate_is_running();
> vm_stop(RUN_STATE_SAVE_VM);
> global_state_store_running();
> @@ -2263,6 +2270,20 @@ void qmp_xen_save_devices_state(const char *filename,
> Error **errp)
> qemu_fclose(f);
> if (ret < 0) {
> error_setg(errp, QERR_IO_ERROR);
> + } else {
> + /* libxl calls the QMP command "stop" before calling
> + * "xen-save-devices-state" and in case of migration failure, libxl
> + * would call "cont".
> + * So call bdrv_inactivate_all (release locks) here to let the other
> + * side of the migration take controle of the images.
> + */
> + if (live && !saved_vm_running) {
> + ret = bdrv_inactivate_all();
> + if (ret) {
> + error_setg(errp, "%s: bdrv_inactivate_all() failed (%d)",
> + __func__, ret);
> + }
> + }
> }
>
> the_end:
> diff --git a/qapi/migration.json b/qapi/migration.json
> index bbc4671ded..03f57c9616 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1075,6 +1075,9 @@
> # data. See xen-save-devices-state.txt for a description of the binary
> # format.
> #
> +# @live: Optional argument to ask QEMU to treat this command as part of a
> live
> +# migration. Default to true. (since 2.11)
> +#
> # Returns: Nothing on success
> #
> # Since: 1.1
> @@ -1086,7 +1089,8 @@
> # <- { "return": {} }
> #
> ##
> -{ 'command': 'xen-save-devices-state', 'data': {'filename': 'str'} }
> +{ 'command': 'xen-save-devices-state',
> + 'data': {'filename': 'str', '*live':'bool' } }
>
> ##
> # @xen-set-replication:
> --
> Anthony PERARD
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK