linux-kernel - Re: [RFC PATCH v3 2/5] KVM: arm64: Add support for PSCI v1.2 and v1.3

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Date: Fri, 22 Mar 2024 16:05:00 +0000
From: Marc Zyngier <maz@...nel.org>
To: David Woodhouse <dwmw2@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org,
	kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	David Woodhouse <dwmw@...zon.co.uk>,
	Mostafa Saleh <smostafa@...gle.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev,
	linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH v3 2/5] KVM: arm64: Add support for PSCI v1.2 and v1.3

On Tue, 19 Mar 2024 12:59:03 +0000,
David Woodhouse <dwmw2@...radead.org> wrote:
> 
> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> Since the v1.3 specification is still in Alpha, only default to v1.2
> unless userspace explicitly requests v1.3 for now.
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---
>  arch/arm64/kvm/hypercalls.c | 2 ++
>  arch/arm64/kvm/psci.c       | 6 +++++-
>  include/kvm/arm_psci.h      | 4 +++-
>  3 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 5763d979d8ca..9c6267ca2b82 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -575,6 +575,8 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  		case KVM_ARM_PSCI_0_2:
>  		case KVM_ARM_PSCI_1_0:
>  		case KVM_ARM_PSCI_1_1:
> +		case KVM_ARM_PSCI_1_2:
> +		case KVM_ARM_PSCI_1_3:
>  			if (!wants_02)
>  				return -EINVAL;
>  			vcpu->kvm->arch.psci_version = val;
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 1f69b667332b..f689ef3f2f10 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -322,7 +322,7 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
>  
>  	switch(psci_fn) {
>  	case PSCI_0_2_FN_PSCI_VERSION:
> -		val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
> +		val = PSCI_VERSION(1, minor);
>  		break;
>  	case PSCI_1_0_FN_PSCI_FEATURES:
>  		arg = smccc_get_arg1(vcpu);
> @@ -449,6 +449,10 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
>  	}
>  
>  	switch (version) {
> +	case KVM_ARM_PSCI_1_3:
> +		return kvm_psci_1_x_call(vcpu, 3);
> +	case KVM_ARM_PSCI_1_2:
> +		return kvm_psci_1_x_call(vcpu, 2);
>  	case KVM_ARM_PSCI_1_1:
>  		return kvm_psci_1_x_call(vcpu, 1);
>  	case KVM_ARM_PSCI_1_0:
> diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
> index e8fb624013d1..ebd7d9a12790 100644
> --- a/include/kvm/arm_psci.h
> +++ b/include/kvm/arm_psci.h
> @@ -14,8 +14,10 @@
>  #define KVM_ARM_PSCI_0_2	PSCI_VERSION(0, 2)
>  #define KVM_ARM_PSCI_1_0	PSCI_VERSION(1, 0)
>  #define KVM_ARM_PSCI_1_1	PSCI_VERSION(1, 1)
> +#define KVM_ARM_PSCI_1_2	PSCI_VERSION(1, 2)
> +#define KVM_ARM_PSCI_1_3	PSCI_VERSION(1, 3)
>  
> -#define KVM_ARM_PSCI_LATEST	KVM_ARM_PSCI_1_1
> +#define KVM_ARM_PSCI_LATEST	KVM_ARM_PSCI_1_2 /* v1.3 is still Alpha */
>  
>  static inline int kvm_psci_version(struct kvm_vcpu *vcpu)
>  {

Consider making the visibility of v1.2/1.3 to userspace and guest the
last patch in the series, so that there is no transient support for
some oddball PSCI version with no feature (keeps bisection clean).

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.