On Mon, Mar 08, 2021 at 02:42:00PM +0000, Marc Zyngier wrote:
> On Fri, 05 Mar 2021 14:36:09 +0000,
> Anshuman Khandual <anshuman.khand...@arm.com> wrote:
> > -   switch (cpuid_feature_extract_unsigned_field(mmfr0, tgran_2)) {
> > -   default:
> > -   case 1:
> > +   tgran_2 = cpuid_feature_extract_unsigned_field(mmfr0, tgran_2_shift);
> > +   if (tgran_2 == ID_AA64MMFR0_TGRAN_2_SUPPORTED_NONE) {
> >             kvm_err("PAGE_SIZE not supported at Stage-2, giving up\n");
> >             return -EINVAL;
> > -   case 0:
> > +   } else if (tgran_2 == ID_AA64MMFR0_TGRAN_2_SUPPORTED_DEFAULT) {
> >             kvm_debug("PAGE_SIZE supported at Stage-2 (default)\n");
> > -           break;
> > -   case 2:
> > +   } else if (tgran_2 >= ID_AA64MMFR0_TGRAN_2_SUPPORTED_MIN &&
> > +              tgran_2 <= ID_AA64MMFR0_TGRAN_2_SUPPORTED_MAX) {
> >             kvm_debug("PAGE_SIZE supported at Stage-2 (advertised)\n");
> > -           break;
> > +   } else {
> > +           kvm_err("Unsupported value, giving up\n");
> > +           return -EINVAL;
> 
> nit: this doesn't say *what* value is unsupported, and I really
> preferred the switch-case version, such as this:
> 
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 1f22b36a0eff..d267e4b1aec6 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -312,15 +312,18 @@ int kvm_set_ipa_limit(void)
>  
>       switch (cpuid_feature_extract_unsigned_field(mmfr0, tgran_2)) {
>       default:
> -     case 1:
> +     case ID_AA64MMFR0_TGRAN_2_SUPPORTED_NONE:
>               kvm_err("PAGE_SIZE not supported at Stage-2, giving up\n");
>               return -EINVAL;
> -     case 0:
> +     case ID_AA64MMFR0_TGRAN_2_SUPPORTED_DEFAULT:
>               kvm_debug("PAGE_SIZE supported at Stage-2 (default)\n");
>               break;
> -     case 2:
> +     case ID_AA64MMFR0_TGRAN_2_SUPPORTED_MIN ... 
> ID_AA64MMFR0_TGRAN_2_SUPPORTED_MAX:
>               kvm_debug("PAGE_SIZE supported at Stage-2 (advertised)\n");
>               break;
> +     default:
> +             kvm_err("Unsupported value for TGRAN_2, giving up\n");
> +             return -EINVAL;
>       }
>  
>       kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
> 
> 
> Otherwise:
> 
> Acked-by: Marc Zyngier <m...@kernel.org>

Anshuman -- please can you spin a v2 with the switch syntax as suggested
above by Marc?

Will

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