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

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Tue, 2024-02-13 at 14:33 +0100, Jan Beulich wrote:
> On 05.02.2024 16:32, Oleksii Kurochko wrote:
> > --- a/xen/arch/riscv/Kconfig
> > +++ b/xen/arch/riscv/Kconfig
> > @@ -45,6 +45,13 @@ config RISCV_ISA_C
> >  
> >       If unsure, say Y.
> >  
> > +config TOOLCHAIN_HAS_ZIHINTPAUSE
> > +   bool
> > +   default y
> 
> Shorter as "def_bool y".
> 
> > +   depends on !64BIT || $(cc-option,-mabi=lp64 -
> > march=rv64ima_zihintpause)
> > +   depends on !32BIT || $(cc-option,-mabi=ilp32 -
> > march=rv32ima_zihintpause)
> 
> So for a reason I cannot really see -mabi= is indeed required here,
> or else the compiler sees an issue with the D extension. But enabling
> both M and A shouldn't really be needed in this check, as being
> unrelated?
Agree, that M and A could be dropped.

Regarding -mabi my guess is because D extension can be emulated by
compiler, doesn't matter if D is set in -march.  If it is set then
hardware instruction will be used, otherwise emulated instruction will
be used.
And if D extenstion is always present it is need to know which ABI
should be used. If D extenstion has h/w support then -mabi should be
also update to lp64d instead of lp64.

> 
> > +   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
> 
> That said, you may or may not be aware that personally I'm against
> encoding such in Kconfig, and my repeated attempts to get the
> respective
> discussion unstuck have not led anywhere. Therefore if you keep this,
> I'll
> be in trouble whether to actually ack the change as a whole.
Could I ask what is wrong with introduction of such things on KConfig?

Would it be better to put everything in riscv/arch.mk?

~ Oleksii