Re: [PATCH v2 3/5] KVM: arm64: Add context-switch of ACCDATA_EL1

[Arnd Bergmann]

On Sun, Oct 25, 2026, at 08:51, Fuad Tabba wrote:
>  	return kvm_has_sctlr2(kern_hyp_va(vcpu->kvm));
>  }
> 
> +static inline bool ctxt_has_accdata(struct kvm_cpu_context *ctxt)
> +{
> +	struct kvm_vcpu *vcpu;
> +
> +	/* The host never uses ACCDATA_EL1 */
> +	if (!cpus_have_final_cap(ARM64_HAS_LS64_ACCDATA) || 
> !ctxt_is_guest(ctxt))
> +		return false;

Maybe add a wrapper for this as we have for other features?

In my patch I've converted the check to use this one now:

--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -909,6 +909,11 @@ static inline bool system_supports_bbml3(void)
        return alternative_has_cap_unlikely(ARM64_HAS_BBML3);
 }
 
+static inline bool system_supports_ls64_accdata(void)
+{
+       return cpus_have_final_cap(ARM64_HAS_LS64_ACCDATA);
+}
+
 int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
 bool try_emulate_mrs(struct pt_regs *regs, u32 isn);

which makes sense to add in your patch first.

I think we'll also want a HWCAP3_LS64_ACCDATA exported to
userspace, but we can keep that separate.

       Arnd