Re: [PATCH V5 12/25] cpr: QMP interfaces for restart

[Steven Sistare <steven.sistare@oracle.com>]

On 7/8/2021 11:49 AM, Marc-André Lureau wrote:
> Hi
> 
> On Wed, Jul 7, 2021 at 9:33 PM Steve Sistare <steven.sistare@oracle.com <mailto:steven.sistare@oracle.com>> wrote:
> 
>     cprexec calls cprexec().  Syntax:
>       { 'command': 'cprexec', 'data': { 'argv': [ 'str' ] } }
> 
>     Add the restart mode:
>       { 'enum': 'CprMode', 'data': [ 'reboot', 'restart' ] }
> 
>     Signed-off-by: Steve Sistare <steven.sistare@oracle.com <mailto:steven.sistare@oracle.com>>
>     ---
>      monitor/qmp-cmds.c |  5 +++++
>      qapi/cpr.json      | 16 +++++++++++++++-
>      2 files changed, 20 insertions(+), 1 deletion(-)
> 
>     diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
>     index 1128604..7326f7d 100644
>     --- a/monitor/qmp-cmds.c
>     +++ b/monitor/qmp-cmds.c
>     @@ -179,6 +179,11 @@ void qmp_cprsave(const char *file, CprMode mode, Error **errp)
>          cprsave(file, mode, errp);
>      }
> 
>     +void qmp_cprexec(strList *args, Error **errp)
>     +{
>     +    cprexec(args, errp);
>     +}
>     +
>      void qmp_cprload(const char *file, Error **errp)
>      {
>          cprload(file, errp);
>     diff --git a/qapi/cpr.json b/qapi/cpr.json
>     index b6fdc89..2467e48 100644
>     --- a/qapi/cpr.json
>     +++ b/qapi/cpr.json
>     @@ -16,10 +16,12 @@
>      #
>      # @reboot: checkpoint can be cprload'ed after a host kexec reboot.
>      #
>     +# @restart: checkpoint can be cprload'ed after restarting qemu.
>     +#
>      # Since: 6.1
>      ##
>      { 'enum': 'CprMode',
>     -  'data': [ 'reboot' ] }
>     +  'data': [ 'reboot', 'restart' ] }
> 
> 
>      ##
>     @@ -61,6 +63,18 @@
>                  'mode': 'CprMode' } }
> 
>      ##
>     +# @cprexec:
>     +#
>     +# Restart qemu.
>     +#
>     +# @argv: arguments to exec
> 
> 
> Why is it not then called cpr-restart ? 

I'll change the description.  exec is the key aspect to convey.

< Why does it take the whole argv? 

It takes the whole argv because the caller may provide a prefix command to
modify the process context before executing qemu.  We do that.

> Could argv be made optional?

If argv is omitted, I could exec the qemu binary with no args, but I don't think that 
would be useful.  It may even be confusing, if the caller has a bug and passes no args;
qemu would start and do nothing, rather than fail with an "exec failed" message.

- Steve

>     +#
>     +# Since: 6.1
>     +##
>     +{ 'command': 'cprexec',
>     +  'data': { 'argv': [ 'str' ] } }
>     +
>     +##
>      # @cprload:
>      #
>      # Start virtual machine from checkpoint file that was created earlier using
>     -- 
>     1.8.3.1
> 
> 
> 
> 
> -- 
> Marc-André Lureau