Re: [RFC v3] VFIO Migration

[Paolo Bonzini <pbonzini@redhat.com>]

On 10/11/20 10:53, Stefan Hajnoczi wrote:
> "allowed_values"
>    The list all values that the device implementation accepts for this migration
>    parameter. Integer ranges can be described using "<min>-<max>" strings.
> 
>    Examples: ['a', 'b', 'c'], [1, 5, 7], ['0-255', 512, '1024-2048'], [true]
> 
>    This member is optional. When absent, any value suitable for the type may be
>    given but the device implementation may refuse certain values.

I'd rather make this simpler:

- remove allowed_values for strings.  Effect: discourages using strings 
as enums, leaving them only for free-form values such as vendor name or 
model name.

- remove allowed_values for bools.  If off_value is absent the only 
allowed value is init_value.  If off_value is present, both true and 
false are allowed (and !off_value is the "on_value", so to speak).

- change allowed_values into allowed_min and allowed_max for int values. 
  Advantage: avoids having to parse strings as ranges.  Disadvantage: 
removes expressiveness (cannot say "x must be a power of two"), but I'm 
not sure it's worth the extra complication.

Thanks,

Paolo

> "description"
>    A human-readable description of the migration parameter. This is not intended
>    for user interfaces but rather as a troubleshooting aid for developers. The
>    description is typically written in English. This member is optional.
> 
> "init_value"
>    The initial parameter value when a device instance is created. This member is
>    required.
> 
> "off_value"
>    The parameter value that disables the effect of this parameter. This member
>    is absent if the migration parameter cannot be disabled.
> 
> "type"
>    The data type ("bool", "int", "str"). This member is required.