Re: [PATCH v4 25/30] xen/riscv: add minimal stuff to processor.h to build full Xen

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.02.2024 12:16, Oleksii wrote:
> On Thu, 2024-02-15 at 17:43 +0100, Jan Beulich wrote:
>> On 15.02.2024 17:38, Oleksii wrote:
>>> On Tue, 2024-02-13 at 14:33 +0100, Jan Beulich wrote:
>>>> On 05.02.2024 16:32, Oleksii Kurochko wrote:
>>>>> + depends on LLD_VERSION >= 150000 || LD_VERSION >=
>>>>> 23600
>>>>
>>>> What's the linker dependency here? Depending on the answer I
>>>> might
>>>> further
>>>> ask why "TOOLCHAIN" when elsewhere we use CC_HAS_ or HAS_CC_ or
>>>> HAS_AS_.
>>> I missed to introduce {L}LLD_VERSION config. It should output from
>>> the
>>> command:
>>>   riscv64-linux-gnu-ld --version
>>
>> Doesn't answer my question though where the linker version matters
>> here.
> Then I misinterpreted your initial question.
> Could you please provide further clarification or rephrase it for
> better understanding?
> 
> Probably, your question was about why linker dependency is needed here,
> then
> it is not sufficient to check if a toolchain supports a particular  
> extension without checking if the linker supports that extension   
> too.
> For example, Clang 15 supports Zihintpause but GNU bintutils
> 2.35.2 does not, leading build errors like so:
>     
>    riscv64-linux-gnu-ld: -march=rv64i_zihintpause2p0: Invalid or
>    unknown z ISA extension: 'zihintpause'

Hmm, that's certainly "interesting" behavior of the RISC-V linker. Yet
isn't the linker capability expected to be tied to that of gas? I would
find it far more natural if a gas dependency existed here. If such a
connection cannot be taken for granted, I'm pretty sure you'd need to
probe both then anyway.

Jan