Re: [PATCH v2 3/8] qapi/misc: Restrict balloon-related commands to machine code

[David Hildenbrand <david@redhat.com>]

On 16.03.20 01:03, Philippe Mathieu-Daudé wrote:
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  qapi/machine.json          | 83 ++++++++++++++++++++++++++++++++++++++
>  qapi/misc.json             | 83 --------------------------------------
>  include/sysemu/balloon.h   |  2 +-
>  balloon.c                  |  2 +-
>  hw/virtio/virtio-balloon.c |  2 +-
>  monitor/hmp-cmds.c         |  1 +
>  6 files changed, 87 insertions(+), 86 deletions(-)
> 
> diff --git a/qapi/machine.json b/qapi/machine.json
> index 07ffc07ba2..c096efbea3 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -915,3 +915,86 @@
>    'data': 'NumaOptions',
>    'allow-preconfig': true
>  }
> +
> +##
> +# @balloon:
> +#
> +# Request the balloon driver to change its balloon size.
> +#
> +# @value: the target size of the balloon in bytes

Not related to your patch. The description of most of this stuff is wrong.

It's not the target size of the balloon, it's the target logical size of
the VM (logical_vm_size = vm_ram_size - balloon_size)

-> balloon_size = vm_ram_size - @value

E.g., "balloon 1024" with a 3G guest means "please inflate the balloon
to 2048"

> +#
> +# Returns: - Nothing on success
> +#          - If the balloon driver is enabled but not functional because the KVM
> +#            kernel module cannot support it, KvmMissingCap
> +#          - If no balloon device is present, DeviceNotActive
> +#
> +# Notes: This command just issues a request to the guest.  When it returns,
> +#        the balloon size may not have changed.  A guest can change the balloon
> +#        size independent of this command.
> +#
> +# Since: 0.14.0
> +#
> +# Example:
> +#
> +# -> { "execute": "balloon", "arguments": { "value": 536870912 } }
> +# <- { "return": {} }
> +#
> +##
> +{ 'command': 'balloon', 'data': {'value': 'int'} }
> +
> +##
> +# @BalloonInfo:
> +#
> +# Information about the guest balloon device.
> +#
> +# @actual: the number of bytes the balloon currently contains

Dito

@actual is the logical size of the VM (logical_vm_size = vm_ram_size -
balloon_size)

> +#
> +# Since: 0.14.0
> +#
> +##
> +{ 'struct': 'BalloonInfo', 'data': {'actual': 'int' } }
> +
> +##
> +# @query-balloon:
> +#
> +# Return information about the balloon device.
> +#
> +# Returns: - @BalloonInfo on success
> +#          - If the balloon driver is enabled but not functional because the KVM
> +#            kernel module cannot support it, KvmMissingCap
> +#          - If no balloon device is present, DeviceNotActive
> +#
> +# Since: 0.14.0
> +#
> +# Example:
> +#
> +# -> { "execute": "query-balloon" }
> +# <- { "return": {
> +#          "actual": 1073741824,
> +#       }
> +#    }
> +#
> +##
> +{ 'command': 'query-balloon', 'returns': 'BalloonInfo' }
> +
> +##
> +# @BALLOON_CHANGE:
> +#
> +# Emitted when the guest changes the actual BALLOON level. This value is
> +# equivalent to the @actual field return by the 'query-balloon' command
> +#
> +# @actual: actual level of the guest memory balloon in bytes

Dito

@actual is the logical size of the VM (vm_ram_size - balloon_size)


Most probably we want to pull this description fix out. #badinterface

-- 
Thanks,

David / dhildenb