Re: [PATCH v2] xen: EXPERT clean-up and introduce UNSUPPORTED

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.11.2020 09:45, Bertrand Marquis wrote:
>> On 18 Nov 2020, at 00:50, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
>> --- a/xen/arch/x86/Kconfig
>> +++ b/xen/arch/x86/Kconfig
>> @@ -102,8 +102,8 @@ config HVM
>>        If unsure, say Y.
>>
>> config XEN_SHSTK
>> -    bool "Supervisor Shadow Stacks"
>> -    depends on HAS_AS_CET_SS && EXPERT
>> +    bool "Supervisor Shadow Stacks (UNSUPPORTED)"
>> +    depends on HAS_AS_CET_SS && UNSUPPORTED
> 
> This one is not following the standard scheme with “if UNSUPPORTED"

There's no standard scheme here: There's one case where the entire
option depends on some other setting (e.g. UNSUPPORTED) and another
where just the prompt (i.e. giving the user a choice) does. The
difference becomes obvious when the option has a default other than
"no": Despite the invisible prompt, it may get turned on. In the
case here (serving as a good example), "default y" would mean the
feature gets turned on when "if UNSUPPORTED" would be added to the
prompt and when UNSUPPORTED is itself off.

Jan