Re: [Qemu-devel] [PATCH v1] linux-user: elf: ELF_HWCAP for s390x

[Richard Henderson <rth@twiddle.net>]

On 6/4/19 4:36 AM, David Hildenbrand wrote:
> +    if (s390_has_feat(S390_FEAT_ESAN3)) {
> +        hwcap |= HWCAP_S390_ESAN3;
> +    }
> +    if (s390_has_feat(S390_FEAT_ZARCH)) {
> +        hwcap |= HWCAP_S390_ZARCH;
> +    }

While it's nice and symetrical testing these two features, I don't think they
can ever be false.

> +    if (s390_has_feat(S390_FEAT_STFLE)) {
> +        hwcap |= HWCAP_S390_STFLE;
> +    }
> +    if (s390_has_feat(S390_FEAT_MSA)) {
> +        hwcap |= HWCAP_S390_MSA;
> +    }
> +    if (s390_has_feat(S390_FEAT_LONG_DISPLACEMENT)) {
> +        hwcap |= HWCAP_S390_LDISP;
> +    }
> +    if (s390_has_feat(S390_FEAT_EXTENDED_IMMEDIATE)) {
> +        hwcap |= HWCAP_S390_EIMM;
> +    }
> +    if (s390_has_feat(S390_FEAT_EXTENDED_TRANSLATION_3) &&
> +        s390_has_feat(S390_FEAT_ETF3_ENH)) {
> +        hwcap |= HWCAP_S390_ETF3EH;
> +    }
> +    /* 31-bit processes can use 64-bit registers */
> +    hwcap |= HWCAP_S390_HIGH_GPRS;

And certainly this could never be set unless ZARCH, otherwise you have no
64-bit registers.  ;-)

So maybe clearer to just start with

  hwcap = HWCAP_S390_ESAN3 | HWCAP_S390_ZARCH | HWCAP_S390_HIGH_GPRS;

and continue from there.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~