[PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

[PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

[Anshuman Khandual]

This replaces multiple open encoding (0x7) with ID_AA64MMFR0_PARANGE_MASK
thus cleaning the clutter. It modifies an existing ID_AA64MMFR0 helper and
introduces a new one i.e id_aa64mmfr0_iparange() and id_aa64mmfr0_parange()
respectively.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kvmarm@lists.cs.columbia.edu

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This applies after (https://patchwork.kernel.org/patch/11541893/).

 arch/arm64/include/asm/cpufeature.h | 11 ++++++++++-
 arch/arm64/kernel/cpufeature.c      |  5 ++---
 arch/arm64/kvm/reset.c              |  9 +++++----
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 1291ad5a9ccb..320cfc5b6025 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -706,8 +706,17 @@ void arm64_set_ssbd_mitigation(bool state);
 
 extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
 
-static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)
+#define ID_AA64MMFR0_PARANGE_MASK 0x7
+
+static inline u32 id_aa64mmfr0_parange(u64 mmfr0)
 {
+	return mmfr0 & ID_AA64MMFR0_PARANGE_MASK;
+}
+
+static inline u32 id_aa64mmfr0_iparange(u64 mmfr0)
+{
+	int parange = id_aa64mmfr0_parange(mmfr0);
+
 	switch (parange) {
 	case 0: return 32;
 	case 1: return 36;
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 30917fe7942a..2c62f7c64a3c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2185,7 +2185,7 @@ static void verify_sve_features(void)
 void verify_hyp_capabilities(void)
 {
 	u64 safe_mmfr1, mmfr0, mmfr1;
-	int parange, ipa_max;
+	int ipa_max;
 	unsigned int safe_vmid_bits, vmid_bits;
 
 	safe_mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
@@ -2201,8 +2201,7 @@ void verify_hyp_capabilities(void)
 	}
 
 	/* Verify IPA range */
-	parange = mmfr0 & 0x7;
-	ipa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
+	ipa_max = id_aa64mmfr0_iparange(mmfr0);
 	if (ipa_max < get_kvm_ipa_limit()) {
 		pr_crit("CPU%d: IPA range mismatch\n", smp_processor_id());
 		cpu_die_early();
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 841b492ff334..2e4da75d79ea 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -347,10 +347,10 @@ u32 get_kvm_ipa_limit(void)
 
 void kvm_set_ipa_limit(void)
 {
-	unsigned int ipa_max, pa_max, va_max, parange;
+	unsigned int ipa_max, pa_max, va_max;
 
-	parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 0x7;
-	pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
+	pa_max = id_aa64mmfr0_iparange(read_sanitised_ftr_reg
+						(SYS_ID_AA64MMFR0_EL1));
 
 	/* 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));
 	if (parange > ID_AA64MMFR0_PARANGE_MAX)
 		parange = ID_AA64MMFR0_PARANGE_MAX;
 	vtcr |= parange << VTCR_EL2_PS_SHIFT;
-- 
2.20.1

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Re: [PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

[Marc Zyngier]

Anshuman,

On 2020-05-12 03:13, Anshuman Khandual wrote:
> This replaces multiple open encoding (0x7) with 
> ID_AA64MMFR0_PARANGE_MASK
> thus cleaning the clutter. It modifies an existing ID_AA64MMFR0 helper 
> and
> introduces a new one i.e id_aa64mmfr0_iparange() and 
> id_aa64mmfr0_parange()
> respectively.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: James Morse <james.morse@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kvmarm@lists.cs.columbia.edu
> 
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This applies after (https://patchwork.kernel.org/patch/11541893/).
> 
>  arch/arm64/include/asm/cpufeature.h | 11 ++++++++++-
>  arch/arm64/kernel/cpufeature.c      |  5 ++---
>  arch/arm64/kvm/reset.c              |  9 +++++----
>  3 files changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cpufeature.h
> b/arch/arm64/include/asm/cpufeature.h
> index 1291ad5a9ccb..320cfc5b6025 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -706,8 +706,17 @@ void arm64_set_ssbd_mitigation(bool state);
> 
>  extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
> 
> -static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)
> +#define ID_AA64MMFR0_PARANGE_MASK 0x7

I still disagree with this 7. Per the letter of the architecture, it
is wrong and should be 0xf, just like any other property described
in an ID register.

> +
> +static inline u32 id_aa64mmfr0_parange(u64 mmfr0)
>  {
> +	return mmfr0 & ID_AA64MMFR0_PARANGE_MASK;
> +}
> +
> +static inline u32 id_aa64mmfr0_iparange(u64 mmfr0)

There is also no such thing as an IPA range in the architecture.
Everything is PA. The only thing that actually describe an IPA
range is what KVM makes of it.

Overall, this patch confuses me more than anything else. I'd rather
you fix ID_AA64MMFR0_PARANGE_MASK to have the right value and be
done with it.

         M.
-- 
Jazz is not dead. It just smells funny...
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Re: [PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

[Mark Rutland]

On Tue, May 12, 2020 at 07:43:26AM +0530, Anshuman Khandual wrote:
> This replaces multiple open encoding (0x7) with ID_AA64MMFR0_PARANGE_MASK
> thus cleaning the clutter. It modifies an existing ID_AA64MMFR0 helper and
> introduces a new one i.e id_aa64mmfr0_iparange() and id_aa64mmfr0_parange()
> respectively.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: James Morse <james.morse@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kvmarm@lists.cs.columbia.edu
> 
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This applies after (https://patchwork.kernel.org/patch/11541893/).
> 
>  arch/arm64/include/asm/cpufeature.h | 11 ++++++++++-
>  arch/arm64/kernel/cpufeature.c      |  5 ++---
>  arch/arm64/kvm/reset.c              |  9 +++++----
>  3 files changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 1291ad5a9ccb..320cfc5b6025 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -706,8 +706,17 @@ void arm64_set_ssbd_mitigation(bool state);
>  
>  extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
>  
> -static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange)
> +#define ID_AA64MMFR0_PARANGE_MASK 0x7

We already have ID_AA64MMFR0_PARANGE_SHIFT in <asm/sysreg.h>, so if we
need this it should live there too.

The ARM ARM tells me ID_AA64MMFR0_EL1.PARange is bits 3:0, so this
should be 0xf.

Given it's a standard 4-bit field, do we even need this? We have helpers
that assume 4 bits for standard fields, e.g.
cpuid_feature_extract_unsigned_field().

> +
> +static inline u32 id_aa64mmfr0_parange(u64 mmfr0)
>  {
> +	return mmfr0 & ID_AA64MMFR0_PARANGE_MASK;
> +}

	return cpuid_feature_extract_unsigned_field(mmfr0,
		ID_AA64MMFR0_PARANGE_SHIFT);

> +
> +static inline u32 id_aa64mmfr0_iparange(u64 mmfr0)
> +{
> +	int parange = id_aa64mmfr0_parange(mmfr0);
> +
>  	switch (parange) {
>  	case 0: return 32;
>  	case 1: return 36;
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 30917fe7942a..2c62f7c64a3c 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -2185,7 +2185,7 @@ static void verify_sve_features(void)
>  void verify_hyp_capabilities(void)
>  {
>  	u64 safe_mmfr1, mmfr0, mmfr1;
> -	int parange, ipa_max;
> +	int ipa_max;
>  	unsigned int safe_vmid_bits, vmid_bits;
>  
>  	safe_mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
> @@ -2201,8 +2201,7 @@ void verify_hyp_capabilities(void)
>  	}
>  
>  	/* Verify IPA range */
> -	parange = mmfr0 & 0x7;
> -	ipa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
> +	ipa_max = id_aa64mmfr0_iparange(mmfr0);

Why drop id_aa64mmfr0_parange_to_phys_shift()?

>  	if (ipa_max < get_kvm_ipa_limit()) {
>  		pr_crit("CPU%d: IPA range mismatch\n", smp_processor_id());
>  		cpu_die_early();
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 841b492ff334..2e4da75d79ea 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -347,10 +347,10 @@ u32 get_kvm_ipa_limit(void)
>  
>  void kvm_set_ipa_limit(void)
>  {
> -	unsigned int ipa_max, pa_max, va_max, parange;
> +	unsigned int ipa_max, pa_max, va_max;
>  
> -	parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 0x7;
> -	pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
> +	pa_max = id_aa64mmfr0_iparange(read_sanitised_ftr_reg
> +						(SYS_ID_AA64MMFR0_EL1));

Weird style here. the '(' should be kept next to the function name.

>
>  	/* 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;
}

... we do similar for the system_supports_xxx() helpers.

Thanks,
Mark.
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Re: [PATCH] arm64/cpufeature: Add ID_AA64MMFR0_PARANGE_MASK

[Mark Rutland]

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.
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