Re: [PATCH V1 03/32] savevm: QMP command for cprsave

[Eric Blake <eblake@redhat.com>]

On 7/30/20 10:14 AM, Steve Sistare wrote:
> To enable live reboot, provide the cprsave QMP command and the VMS_REBOOT
> vmstate-saving operation, which saves the state of the virtual machine in a
> simple file.
> 
> Syntax:
>    {'command':'cprsave', 'data':{'file':'str', 'mode':'str'}}
> 
>    The mode argument must be 'reboot'.  Additional modes will be defined in
>    the future.
> 

Focusing on just the UI:

> +++ b/qapi/migration.json
> @@ -1621,3 +1621,17 @@
>   ##
>   { 'event': 'UNPLUG_PRIMARY',
>     'data': { 'device-id': 'str' } }
> +
> +##
> +# @cprsave:
> +#
> +# Create a checkpoint of the virtual machine device state in @file.
> +# Guest RAM and guest block device blocks are not saved.
> +#
> +# @file: name of checkpoint file

Since you used qemu_open() in the code, this can include a 
'/dev/fdset/NNN' magic name for saving into a previously-passed-in file 
descriptor instead of directly opening a local file name.  That's a good 
thing, but I don't know if it needs explicit mention in the docs.

> +# @mode: 'reboot' : checkpoint can be cprload'ed after a host kexec reboot.
> +#
> +# Since 5.0

5.2 (you've missed 5.0 by a long shot, and even 5.1 is too late now).

> +##
> +{ 'command': 'cprsave', 'data': { 'file': 'str', 'mode': 'str' } }

'mode' should be an enum type, rather than an open-coded string:

{ 'enum': 'CprMode', 'data': ['reboot'] }
{ 'command': 'cprsave', 'data': {'file': 'str', 'mode': 'CprMode' } }

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org