linux-kernel - Re: [PATCH 14/14] arm64: KVM: Add ARCH_WORKAROUND_2 discovery through ARCH_FEATURES_FUNC

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Date:   Thu, 24 May 2018 13:25:37 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH 14/14] arm64: KVM: Add ARCH_WORKAROUND_2 discovery
 through ARCH_FEATURES_FUNC_ID

On Tue, May 22, 2018 at 04:06:48PM +0100, Marc Zyngier wrote:
> Now that all our infrastructure is in place, let's expose the
> availability of ARCH_WORKAROUND_2 to guests. We take this opportunity
> to tidy up a couple of SMCCC constants.
> 
> Acked-by: Christoffer Dall <christoffer.dall@....com>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>

Reviewed-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm/include/asm/kvm_host.h   | 12 ++++++++++++
>  arch/arm64/include/asm/kvm_host.h | 23 +++++++++++++++++++++++
>  arch/arm64/kvm/reset.c            |  4 ++++
>  virt/kvm/arm/psci.c               | 18 ++++++++++++++++--
>  4 files changed, 55 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index c7c28c885a19..d478766b56c1 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -315,6 +315,18 @@ static inline bool kvm_arm_harden_branch_predictor(void)
>  	return false;
>  }
>  
> +#define KVM_SSBD_UNKNOWN		-1
> +#define KVM_SSBD_FORCE_DISABLE		0
> +#define KVM_SSBD_EL1_ENTRY		1
> +#define KVM_SSBD_FORCE_ENABLE		2
> +#define KVM_SSBD_MITIGATED		3
> +
> +static inline int kvm_arm_have_ssbd(void)
> +{
> +	/* No way to detect it yet, pretend it is not there. */
> +	return KVM_SSBD_UNKNOWN;
> +}
> +
>  static inline void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu) {}
>  static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
>  
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 9bef3f69bdcd..082b0dbb85c6 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -455,6 +455,29 @@ static inline bool kvm_arm_harden_branch_predictor(void)
>  	return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR);
>  }
>  
> +#define KVM_SSBD_UNKNOWN		-1
> +#define KVM_SSBD_FORCE_DISABLE		0
> +#define KVM_SSBD_EL1_ENTRY		1
> +#define KVM_SSBD_FORCE_ENABLE		2
> +#define KVM_SSBD_MITIGATED		3
> +
> +static inline int kvm_arm_have_ssbd(void)
> +{
> +	switch (arm64_get_ssbd_state()) {
> +	case ARM64_SSBD_FORCE_DISABLE:
> +		return KVM_SSBD_FORCE_DISABLE;
> +	case ARM64_SSBD_EL1_ENTRY:
> +		return KVM_SSBD_EL1_ENTRY;
> +	case ARM64_SSBD_FORCE_ENABLE:
> +		return KVM_SSBD_FORCE_ENABLE;
> +	case ARM64_SSBD_MITIGATED:
> +		return KVM_SSBD_MITIGATED;
> +	case ARM64_SSBD_UNKNOWN:
> +	default:
> +		return KVM_SSBD_UNKNOWN;
> +	}
> +}
> +
>  void kvm_vcpu_load_sysregs(struct kvm_vcpu *vcpu);
>  void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
>  
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 3256b9228e75..20a7dfee8494 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -122,6 +122,10 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>  	/* Reset PMU */
>  	kvm_pmu_vcpu_reset(vcpu);
>  
> +	/* Default workaround setup is enabled (if supported) */
> +	if (kvm_arm_have_ssbd() == KVM_SSBD_EL1_ENTRY)
> +		vcpu->arch.workaround_flags |= VCPU_WORKAROUND_2_FLAG;
> +
>  	/* Reset timer */
>  	return kvm_timer_vcpu_reset(vcpu);
>  }
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
> index c4762bef13c6..4843bfa1f986 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -405,7 +405,7 @@ static int kvm_psci_call(struct kvm_vcpu *vcpu)
>  int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  {
>  	u32 func_id = smccc_get_function(vcpu);
> -	u32 val = PSCI_RET_NOT_SUPPORTED;
> +	u32 val = SMCCC_RET_NOT_SUPPORTED;
>  	u32 feature;
>  
>  	switch (func_id) {
> @@ -417,7 +417,21 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  		switch(feature) {
>  		case ARM_SMCCC_ARCH_WORKAROUND_1:
>  			if (kvm_arm_harden_branch_predictor())
> -				val = 0;
> +				val = SMCCC_RET_SUCCESS;
> +			break;
> +		case ARM_SMCCC_ARCH_WORKAROUND_2:
> +			switch (kvm_arm_have_ssbd()) {
> +			case KVM_SSBD_FORCE_DISABLE:
> +			case KVM_SSBD_UNKNOWN:
> +				break;
> +			case KVM_SSBD_EL1_ENTRY:
> +				val = SMCCC_RET_SUCCESS;
> +				break;
> +			case KVM_SSBD_FORCE_ENABLE:
> +			case KVM_SSBD_MITIGATED:
> +				val = SMCCC_RET_NOT_REQUIRED;
> +				break;
> +			}
>  			break;
>  		}
>  		break;
> -- 
> 2.14.2
>