Re: [PATCH 3/3] semihosting: Restrict to TCG

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 30/5/24 09:31, Paolo Bonzini wrote:
> On Thu, May 30, 2024 at 9:22 AM Philippe Mathieu-Daudé
> <philmd@linaro.org> wrote:
>>
>> On 30/5/24 08:02, Paolo Bonzini wrote:
>>> On Wed, May 29, 2024 at 5:56 PM Philippe Mathieu-Daudé
>>> <philmd@linaro.org> wrote:
>>>> It is pointless to build semihosting when TCG is not available.
>>>
>>> Why? I would have naively assumed that a suitable semihosting API
>>> could be implemented by KVM. The justification (and thus the commit
>>> message) needs to be different for each architecture if it's a matter
>>> of instruction set or insufficient KVM userspace API.
>>
>> I wasn't sure where semihosting could be used so asked on IRC and
>> Alex told me TCG only. Maybe the current implementation is TCG
>> only, and I can reword. It certainly need some refactor to work
>> on KVM, because currently semihosting end calling the TCG probe_access
>> API, which I'm trying to restrict to TCG in order to ease linking
>> multiple libtcg for the single binary (see
>> https://lore.kernel.org/qemu-devel/20240529155918.6221-1-philmd@linaro.org/).
> 
> Ok, that goes in the commit message though.
> 
> "Semihosting currently uses the TCG probe_access API. It is pointless
> to have it in the binary when TCG isn't".
> 
> and in the first two patches:
> 
> "Semihosting currently uses the TCG probe_access API. To prepare for
> encoding the TCG dependency in Kconfig, do not enable it unless TCG is
> available".
> 
> But then, "select FOO if TCG" mean that it can be compiled out; so
> perhaps "imply SEMIHOSTING if TCG" is better? Same for RISC-V's
> "select ARM_COMPATIBLE_SEMIHOSTING if TCG".

You are right. Thanks for reminding me Kconfig "imply" :)

Regards,

Phil.