Re: [PATCH for 4-21 v4] xen/riscv: identify specific ISA supported by cpu

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 2/4/25 12:47 PM, Jan Beulich wrote:

> > +const struct riscv_isa_ext_data __initconst riscv_isa_ext[] = {
> > +    RISCV_ISA_EXT_DATA(i, RISCV_ISA_EXT_i),
> > +    RISCV_ISA_EXT_DATA(m, RISCV_ISA_EXT_m),
> > +    RISCV_ISA_EXT_DATA(a, RISCV_ISA_EXT_a),
> > +    RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
> > +    RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
> > +    RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
> > +    RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
> > +    RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
> > +    RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),
> > +    RISCV_ISA_EXT_DATA(zifencei, RISCV_ISA_EXT_ZIFENCEI),
> > +    RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
> > +    RISCV_ISA_EXT_DATA(zihpm, RISCV_ISA_EXT_ZIHPM),
> > +    RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
> > +    RISCV_ISA_EXT_DATA(smaia, RISCV_ISA_EXT_SMAIA),
> > +    RISCV_ISA_EXT_DATA(ssaia, RISCV_ISA_EXT_SSAIA),
> > +};
> > +
> > +static const struct riscv_isa_ext_data __initconst required_extensions[] = {
> > +    RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),
> > +    RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
> > +    RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
> > +};
> Coming back to my earlier question regarding the B (pseudo-)extension:
> Since riscv_isa_ext[] only contains Zbb, is it precluded anywhere in
> the spec that DT may mention just B when all of its constituents are
> supported?
>
> Which gets me on to G, which is somewhat similar in nature to B. We
> require G when RISCV_ISA_RV64G=y, yet required_extensions[] doesn't
> name it or its constituents. Much like we require C when RISCV_ISA_C=y,
> yet it's not in the table.
>     
Another one thing I am thinking about if we really need a separate required_extensions[] array.

We can leave only riscv_isa_ext[] and then just do a check:
 bitmap_weight(riscv_isa, ...) == ARRAY_SIZE(riscv_isa_ext)

~ Oleksii