linux-kernel - Re: [PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE

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Date:   Tue, 12 May 2020 11:56:14 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

On Tue, May 12, 2020 at 11:53:43AM +0100, Mark Rutland wrote:
> >
> >  	/* Clamp the IPA limit to the PA size supported by the kernel */
> >  	ipa_max = (pa_max > PHYS_MASK_SHIFT) ? PHYS_MASK_SHIFT : pa_max;
> > @@ -411,7 +411,8 @@ int kvm_arm_setup_stage2(struct kvm *kvm, unsigned long type)
> >  		phys_shift = KVM_PHYS_SHIFT;
> >  	}
> >  
> > -	parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 7;
> > +	parange = id_aa64mmfr0_parange(read_sanitised_ftr_reg
> > +						(SYS_ID_AA64MMFR0_EL1));
> 
> Can't we add a system_ipa_range() helper, and avoid more boilerplate in
> each of these?
> 
> e.g.
> 
> int system_ipa_range(void)
> {
> 	u64 mmfr0;
> 	int parange;
> 
> 	mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
> 	parange = cpuid_feature_extract_unsigned_field(mmfr0,
> 		ID_AA64MMFR0_PARANGE_SHIFT);
> 	
> 	return parange;
> }

As Per MarcZ's comments, that should be system_pa_range() rather than
system_ipa_range().

Mark.