Re: [PATCH 2/3] KVM: arm64: selftests: Remove ARM64_FEATURE_FIELD_BITS and its last user

[Oliver Upton <oliver.upton@linux.dev>]

Hi Ben,

On Tue, Oct 14, 2025 at 11:21:07AM +0100, Ben Horgan wrote:
> ARM64_FEATURE_FIELD_BITS is set to 4 but not all ID register fields are 4
> bits. See for instance ID_AA64SMFR0_EL1. The last user of this define,
> ARM64_FEATURE_FIELD_BITS, is the set_id_regs selftest. Its logic assumes
> the fields aren't a single bits; assert that's the case and stop using the
> define. As there are no more users, ARM64_FEATURE_FIELD_BITS is removed.
> 
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
> ---
>  arch/arm64/include/asm/sysreg.h                 | 2 --
>  tools/testing/selftests/kvm/arm64/set_id_regs.c | 8 ++++++--
>  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 6455db1b54fd..d9aa76d08e13 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -1129,8 +1129,6 @@
>  #define gicr_insn(insn)			read_sysreg_s(GICV5_OP_GICR_##insn)
>  #define gic_insn(v, insn)		write_sysreg_s(v, GICV5_OP_GIC_##insn)
>  
> -#define ARM64_FEATURE_FIELD_BITS	4
> -
>  #ifdef __ASSEMBLY__
>  
>  	.macro	mrs_s, rt, sreg

You can send this diff as a separate patch. Selftests actually uses the
definition from tools/arch/arm64/include/asm/sysreg.h, so you'll want to
drop that definition along with the change to set_id_regs.

Thanks,
Oliver