Re: [PATCH v4 06/13] KVM: arm64: Add standard hypervisor firmware register

[Oliver Upton <oupton@google.com>]

On Thu, Feb 24, 2022 at 05:25:52PM +0000, Raghavendra Rao Ananta wrote:
> Introduce the firmware register to hold the standard hypervisor
> service calls (owner value 5) as a bitmap. The bitmap represents
> the features that'll be enabled for the guest, as configured by
> the user-space. Currently, this includes support only for
> Paravirtualized time, represented by bit-0.
> 
> The register is also added to the kvm_arm_vm_scope_fw_regs[] list
> as it maintains its state per-VM.
> 
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
>  arch/arm64/include/asm/kvm_host.h |  2 ++
>  arch/arm64/include/uapi/asm/kvm.h |  4 ++++
>  arch/arm64/kvm/guest.c            |  1 +
>  arch/arm64/kvm/hypercalls.c       | 20 +++++++++++++++++++-
>  include/kvm/arm_hypercalls.h      |  3 +++
>  5 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1909ced3208f..318148b69279 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -105,9 +105,11 @@ struct kvm_arch_memory_slot {
>   * struct kvm_hvc_desc: KVM ARM64 hypercall descriptor
>   *
>   * @hvc_std_bmap: Bitmap of standard secure service calls
> + * @hvc_std_hyp_bmap: Bitmap of standard hypervisor service calls
>   */
>  struct kvm_hvc_desc {
>  	u64 hvc_std_bmap;
> +	u64 hvc_std_hyp_bmap;
>  };
>  
>  struct kvm_arch {
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 2decc30d6b84..9a2caead7359 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -295,6 +295,10 @@ struct kvm_arm_copy_mte_tags {
>  #define KVM_REG_ARM_STD_BIT_TRNG_V1_0		BIT(0)
>  #define KVM_REG_ARM_STD_BMAP_BIT_MAX		0       /* Last valid bit */
>  
> +#define KVM_REG_ARM_STD_HYP_BMAP		KVM_REG_ARM_FW_BMAP_REG(1)
> +#define KVM_REG_ARM_STD_HYP_BIT_PV_TIME		BIT(0)
> +#define KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX	0       /* Last valid bit */
> +
>  /* SVE registers */
>  #define KVM_REG_ARM64_SVE		(0x15 << KVM_REG_ARM_COPROC_SHIFT)
>  
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index d66e6c742bbe..c42426d6137e 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -66,6 +66,7 @@ static const u64 kvm_arm_vm_scope_fw_regs[] = {
>  	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1,
>  	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
>  	KVM_REG_ARM_STD_BMAP,
> +	KVM_REG_ARM_STD_HYP_BMAP,
>  };
>  
>  /**
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 48c126c3da72..ebc0cc26cf2e 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -75,6 +75,10 @@ static bool kvm_hvc_call_supported(struct kvm_vcpu *vcpu, u32 func_id)
>  	case ARM_SMCCC_TRNG_RND64:
>  		return kvm_arm_fw_reg_feat_enabled(hvc_desc->hvc_std_bmap,
>  						KVM_REG_ARM_STD_BIT_TRNG_V1_0);
> +	case ARM_SMCCC_HV_PV_TIME_FEATURES:
> +	case ARM_SMCCC_HV_PV_TIME_ST:
> +		return kvm_arm_fw_reg_feat_enabled(hvc_desc->hvc_std_hyp_bmap,
> +					KVM_REG_ARM_STD_HYP_BIT_PV_TIME);
>  	default:
>  		/* By default, allow the services that aren't listed here */
>  		return true;
> @@ -83,6 +87,7 @@ static bool kvm_hvc_call_supported(struct kvm_vcpu *vcpu, u32 func_id)
>  
>  int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  {
> +	struct kvm_hvc_desc *hvc_desc = &vcpu->kvm->arch.hvc_desc;
>  	u32 func_id = smccc_get_function(vcpu);
>  	u64 val[4] = {SMCCC_RET_NOT_SUPPORTED};
>  	u32 feature;
> @@ -134,7 +139,10 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>  			}
>  			break;
>  		case ARM_SMCCC_HV_PV_TIME_FEATURES:
> -			val[0] = SMCCC_RET_SUCCESS;
> +			if (kvm_arm_fw_reg_feat_enabled(
> +					hvc_desc->hvc_std_hyp_bmap,

It is probably OK to keep this parameter on the line above (just stay
under 100 characters a line).

> +					KVM_REG_ARM_STD_HYP_BIT_PV_TIME))
> +				val[0] = SMCCC_RET_SUCCESS;
>  			break;
>  		}
>  		break;
> @@ -179,6 +187,7 @@ static const u64 kvm_arm_fw_reg_ids[] = {
>  	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1,
>  	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
>  	KVM_REG_ARM_STD_BMAP,
> +	KVM_REG_ARM_STD_HYP_BMAP,
>  };
>  
>  void kvm_arm_init_hypercalls(struct kvm *kvm)
> @@ -186,6 +195,7 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
>  	struct kvm_hvc_desc *hvc_desc = &kvm->arch.hvc_desc;
>  
>  	hvc_desc->hvc_std_bmap = ARM_SMCCC_STD_FEATURES;
> +	hvc_desc->hvc_std_hyp_bmap = ARM_SMCCC_STD_HYP_FEATURES;
>  }
>  
>  int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
> @@ -272,6 +282,9 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  	case KVM_REG_ARM_STD_BMAP:
>  		val = READ_ONCE(hvc_desc->hvc_std_bmap);
>  		break;
> +	case KVM_REG_ARM_STD_HYP_BMAP:
> +		val = READ_ONCE(hvc_desc->hvc_std_hyp_bmap);
> +		break;
>  	default:
>  		return -ENOENT;
>  	}
> @@ -294,6 +307,10 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
>  		fw_reg_bmap = &hvc_desc->hvc_std_bmap;
>  		fw_reg_features = ARM_SMCCC_STD_FEATURES;
>  		break;
> +	case KVM_REG_ARM_STD_HYP_BMAP:
> +		fw_reg_bmap = &hvc_desc->hvc_std_hyp_bmap;
> +		fw_reg_features = ARM_SMCCC_STD_HYP_FEATURES;
> +		break;
>  	default:
>  		return -ENOENT;
>  	}
> @@ -398,6 +415,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  
>  		return 0;
>  	case KVM_REG_ARM_STD_BMAP:
> +	case KVM_REG_ARM_STD_HYP_BMAP:
>  		return kvm_arm_set_fw_reg_bmap(vcpu, reg_id, val);
>  	default:
>  		return -ENOENT;
> diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
> index 64d30b452809..a1cb6e839c74 100644
> --- a/include/kvm/arm_hypercalls.h
> +++ b/include/kvm/arm_hypercalls.h
> @@ -9,6 +9,9 @@
>  #define ARM_SMCCC_STD_FEATURES \
>  	GENMASK_ULL(KVM_REG_ARM_STD_BMAP_BIT_MAX, 0)
>  
> +#define ARM_SMCCC_STD_HYP_FEATURES \
> +	GENMASK_ULL(KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX, 0)
> +
>  int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
>  
>  static inline u32 smccc_get_function(struct kvm_vcpu *vcpu)
> -- 
> 2.35.1.473.g83b2b277ed-goog
> 

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