Re: [PATCH V5 04/22] xen/ioreq: Make x86's IOREQ feature common

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.01.2021 12:01, Oleksandr wrote:
> On 27.01.21 22:46, Stefano Stabellini wrote:
>> On Wed, 27 Jan 2021, Oleksandr wrote:
>>> Thank you. I got a request to make a possibility for user to select IOREQ 
>>> via
>>> the menuconfig on Arm. Saying tech preview do you mean that I also need to 
>>> put
>>> it under CONFIG_EXPERT on Arm?
>> Normally I would say that unless it actually takes an expert to enable
>> the feature, it is better to make it depend on CONFIG_UNSUPPORTED [1].
>>
>> However, in this case, it might actually take an expert :-)
>> Additional patches are still required to enable the feature at the
>> toolstack level, and also the user needs to build a userspace ioreq
>> server. So in this case I am fine either way. I'll leave it up to you
>> and Julien to pick the best one.
>>
>> Either way, please add "(EXPERT)" or "(UNSUPPORTED)" in the one-line
>> kconfig description for ARM if possible.
>>
>>
>> [1] https://marc.info/?l=xen-devel&m=161168780401884
> 
> Thank you for the explanation, personally I would prefer EXPERT, but...
> 
> It would be really nice if we could agreed regarding that *common* 
> Kconfig option before I submit V6 (which would probably avoid me to send 
> V7 I hope).
> 
> Now I see it as following (please note, it is a subject for new patch in 
> this series, which should come last):
> 
> +++ b/xen/common/Kconfig
> @@ -137,7 +137,13 @@ config HYPFS_CONFIG
>            want to hide the .config contents from dom0.
> 
>   config IOREQ_SERVER
> -       bool
> +       bool "IOREQ support" if EXPERT || X86

This would make the prompt visible for x86, which we don't
want. But I guess Stefano was anyway after ...

> +       default X86
> +       depends on HVM
> +       ---help---
> +         Enables generic mechanism for providing emulated devices to 
> the guests.
> +
> +         If unsure, say Y.

 config IOREQ_SERVER
       bool "IOREQ support (EXPERT)" if EXPERT && !X86
       default X86
       depends on HVM

As the prompt should be invisible this way on x86, the (EXPERT)
doesn't need further qualifying, except maybe in the help text
(just to avoid this being taken as a possible mistake).

Jan