Re: [PATCH v5 04/10] KVM: arm64: Add vendor hypervisor firmware register

From: Gavin Shan <gshan@redhat.com>
To: Raghavendra Rao Ananta <rananta@google.com>,
	Marc Zyngier <maz@kernel.org>, Andrew Jones <drjones@redhat.com>,
	James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: kvm@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
	Peter Shier <pshier@google.com>,
	linux-kernel@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 04/10] KVM: arm64: Add vendor hypervisor firmware register
Date: Wed, 13 Apr 2022 11:59:35 +0800	[thread overview]
Message-ID: <06b7539f-c5c0-843d-7617-a35a9f1d0e60@redhat.com> (raw)
In-Reply-To: <20220407011605.1966778-5-rananta@google.com>

Hi Raghavendra,

On 4/7/22 9:15 AM, Raghavendra Rao Ananta wrote:
> Introduce the firmware register to hold the vendor specific
> hypervisor service calls (owner value 6) 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 for KVM-vendor features, and Precision Time
> Protocol (PTP), represented by bit-0 and bit-1 respectively.
> 
> 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/hypercalls.c       | 21 +++++++++++++++++----
>   include/kvm/arm_hypercalls.h      |  4 ++++
>   4 files changed, 27 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 20165242ebd9..b79161bad69a 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -106,10 +106,12 @@ struct kvm_arch_memory_slot {
>    *
>    * @std_bmap: Bitmap of standard secure service calls
>    * @std_hyp_bmap: Bitmap of standard hypervisor service calls
> + * @vendor_hyp_bmap: Bitmap of vendor specific hypervisor service calls
>    */
>   struct kvm_smccc_features {
>   	u64 std_bmap;
>   	u64 std_hyp_bmap;
> +	u64 vendor_hyp_bmap;
>   };
>   
>   struct kvm_arch {
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 67353bf4e69d..9a5ac0ed4113 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -344,6 +344,10 @@ struct kvm_arm_copy_mte_tags {
>   #define KVM_REG_ARM_STD_HYP_BMAP		KVM_REG_ARM_FW_FEAT_BMAP_REG(1)
>   #define KVM_REG_ARM_STD_HYP_BIT_PV_TIME		BIT(0)
>   
> +#define KVM_REG_ARM_VENDOR_HYP_BMAP		KVM_REG_ARM_FW_FEAT_BMAP_REG(2)
> +#define KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT	BIT(0)
> +#define KVM_REG_ARM_VENDOR_HYP_BIT_PTP		BIT(1)
> +
>   /* Device Control API: ARM VGIC */
>   #define KVM_DEV_ARM_VGIC_GRP_ADDR	0
>   #define KVM_DEV_ARM_VGIC_GRP_DIST_REGS	1
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 64ae6c7e7145..80836c341fd3 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -66,8 +66,6 @@ static const u32 hvc_func_default_allowed_list[] = {
>   	ARM_SMCCC_VERSION_FUNC_ID,
>   	ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
>   	ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID,
> -	ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID,
> -	ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID,
>   };
>   
>   static bool kvm_hvc_call_default_allowed(struct kvm_vcpu *vcpu, u32 func_id)
> @@ -102,6 +100,12 @@ static bool kvm_hvc_call_allowed(struct kvm_vcpu *vcpu, u32 func_id)
>   	case ARM_SMCCC_HV_PV_TIME_ST:
>   		return kvm_arm_fw_reg_feat_enabled(smccc_feat->std_hyp_bmap,
>   					KVM_REG_ARM_STD_HYP_BIT_PV_TIME);
> +	case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
> +		return kvm_arm_fw_reg_feat_enabled(smccc_feat->vendor_hyp_bmap,
> +					KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT);
> +	case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
> +		return kvm_arm_fw_reg_feat_enabled(smccc_feat->vendor_hyp_bmap,
> +					KVM_REG_ARM_VENDOR_HYP_BIT_PTP);
>   	default:
>   		return kvm_hvc_call_default_allowed(vcpu, func_id);
>   	}

I guess we may return SMCCC_RET_NOT_SUPPORTED for ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID
if KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT isn't set? Otherwise, we need explain it
in the commit log.

KVM_REG_ARM_VENDOR_HYP_BIT_{FUNC_FEAT, PTP} aren't parallel to each other.
I think PTP can't be on if KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT is off.

> @@ -194,8 +198,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>   		val[3] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3;
>   		break;
>   	case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
> -		val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
> -		val[0] |= BIT(ARM_SMCCC_KVM_FUNC_PTP);
> +		val[0] = smccc_feat->vendor_hyp_bmap;
>   		break;
>   	case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
>   		kvm_ptp_get_time(vcpu, val);
> @@ -222,6 +225,7 @@ static const u64 kvm_arm_fw_reg_ids[] = {
>   	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3,
>   	KVM_REG_ARM_STD_BMAP,
>   	KVM_REG_ARM_STD_HYP_BMAP,
> +	KVM_REG_ARM_VENDOR_HYP_BMAP,
>   };
>   
>   void kvm_arm_init_hypercalls(struct kvm *kvm)
> @@ -230,6 +234,7 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
>   
>   	smccc_feat->std_bmap = KVM_ARM_SMCCC_STD_FEATURES;
>   	smccc_feat->std_hyp_bmap = KVM_ARM_SMCCC_STD_HYP_FEATURES;
> +	smccc_feat->vendor_hyp_bmap = KVM_ARM_SMCCC_VENDOR_HYP_FEATURES;
>   }
>   
>   int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
> @@ -322,6 +327,9 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>   	case KVM_REG_ARM_STD_HYP_BMAP:
>   		val = READ_ONCE(smccc_feat->std_hyp_bmap);
>   		break;
> +	case KVM_REG_ARM_VENDOR_HYP_BMAP:
> +		val = READ_ONCE(smccc_feat->vendor_hyp_bmap);
> +		break;
>   	default:
>   		return -ENOENT;
>   	}
> @@ -348,6 +356,10 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
>   		fw_reg_bmap = &smccc_feat->std_hyp_bmap;
>   		fw_reg_features = KVM_ARM_SMCCC_STD_HYP_FEATURES;
>   		break;
> +	case KVM_REG_ARM_VENDOR_HYP_BMAP:
> +		fw_reg_bmap = &smccc_feat->vendor_hyp_bmap;
> +		fw_reg_features = KVM_ARM_SMCCC_VENDOR_HYP_FEATURES;
> +		break;
>   	default:
>   		return -ENOENT;
>   	}

If KVM_REG_ARM_VENDOR_HYP_BIT_{FUNC_FEAT, PTP} aren't parallel to each other,
special code is needed to gurantee PTP is cleared if VENDOR_HYP is disabled.

> @@ -453,6 +465,7 @@ 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:
> +	case KVM_REG_ARM_VENDOR_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 b0915d8c5b81..eaf4f6b318a8 100644
> --- a/include/kvm/arm_hypercalls.h
> +++ b/include/kvm/arm_hypercalls.h
> @@ -9,6 +9,7 @@
>   /* Last valid bits of the bitmapped firmware registers */
>   #define KVM_REG_ARM_STD_BMAP_BIT_MAX		0
>   #define KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX	0
> +#define KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX	1
>   
>   #define KVM_ARM_SMCCC_STD_FEATURES \
>   	GENMASK_ULL(KVM_REG_ARM_STD_BMAP_BIT_MAX, 0)
> @@ -16,6 +17,9 @@
>   #define KVM_ARM_SMCCC_STD_HYP_FEATURES \
>   	GENMASK_ULL(KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX, 0)
>   
> +#define KVM_ARM_SMCCC_VENDOR_HYP_FEATURES \
> +	GENMASK_ULL(KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX, 0)
> +
>   int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
>   
>   static inline u32 smccc_get_function(struct kvm_vcpu *vcpu)
> 

Thanks,
Gavin

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