Re: [PATCH v6 07/43] arm64: RME: Define the user ABI

[Gavin Shan <gshan@redhat.com>]

On 12/13/24 1:55 AM, Steven Price wrote:
> There is one (multiplexed) CAP which can be used to create, populate and
> then activate the realm.
> 
> Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes from v5:
>   * Actually expose the new VCPU capability (KVM_ARM_VCPU_REC) by bumping
>     KVM_VCPU_MAX_FEATURES - note this also exposes KVM_ARM_VCPU_HAS_EL2!
> ---
>   Documentation/virt/kvm/api.rst    |  1 +
>   arch/arm64/include/uapi/asm/kvm.h | 49 +++++++++++++++++++++++++++++++
>   include/uapi/linux/kvm.h          | 12 ++++++++
>   3 files changed, 62 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 454c2aaa155e..df4679415a4c 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5088,6 +5088,7 @@ Recognised values for feature:
>   
>     =====      ===========================================
>     arm64      KVM_ARM_VCPU_SVE (requires KVM_CAP_ARM_SVE)
> +  arm64      KVM_ARM_VCPU_REC (requires KVM_CAP_ARM_RME)
>     =====      ===========================================
>   
>   Finalizes the configuration of the specified vcpu feature.
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 66736ff04011..8810719523ec 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -108,6 +108,7 @@ struct kvm_regs {
>   #define KVM_ARM_VCPU_PTRAUTH_ADDRESS	5 /* VCPU uses address authentication */
>   #define KVM_ARM_VCPU_PTRAUTH_GENERIC	6 /* VCPU uses generic authentication */
>   #define KVM_ARM_VCPU_HAS_EL2		7 /* Support nested virtualization */
> +#define KVM_ARM_VCPU_REC		8 /* VCPU REC state as part of Realm */
>   
>   struct kvm_vcpu_init {
>   	__u32 target;
> @@ -418,6 +419,54 @@ enum {
>   #define   KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES	3
>   #define   KVM_DEV_ARM_ITS_CTRL_RESET		4
>   
> +/* KVM_CAP_ARM_RME on VM fd */
> +#define KVM_CAP_ARM_RME_CONFIG_REALM		0
> +#define KVM_CAP_ARM_RME_CREATE_RD		1
> +#define KVM_CAP_ARM_RME_INIT_IPA_REALM		2
> +#define KVM_CAP_ARM_RME_POPULATE_REALM		3
> +#define KVM_CAP_ARM_RME_ACTIVATE_REALM		4
> +

I guess it would be nice to rename KVM_CAP_ARM_RME_CREATE_RD to KVM_CAP_ARM_RME_CREATE_REALM
since it's to create a realm. All other macros have suffix "_REALM". Besides, KVM_CAP_ARM_RME_INIT_IPA_REALM
would be KVM_CAP_ARM_RME_INIT_REALM_IPA, and KVM_CAP_ARM_RME_POPULATE_REALM would be
KVM_CAP_ARM_RME_POPULATE_REALM_IPA. Something like below.

/* KVM_CAP_ARM_RME on VM fd */
#define KVM_CAP_ARM_RME_CONFIG_REALM		0
#define KVM_CAP_ARM_RME_CREATE_RD		1
#define KVM_CAP_ARM_RME_INIT_REALM_IPA		2
#define KVM_CAP_ARM_RME_POPULATE_REALM_IPA	3
#define KVM_CAP_ARM_RME_ACTIVATE_REALM		4

> +#define KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA256		0
> +#define KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA512		1
> +
> +#define KVM_CAP_ARM_RME_RPV_SIZE 64
> +
> +/* List of configuration items accepted for KVM_CAP_ARM_RME_CONFIG_REALM */
> +#define KVM_CAP_ARM_RME_CFG_RPV			0
> +#define KVM_CAP_ARM_RME_CFG_HASH_ALGO		1
> +

The comments for the list of configuration items accepted for KVM_CAP_ARM_RME_CONFIG_REALM,
it shall be moved before KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA256 to cover all the definitions
applied to KVM_CAP_ARM_RME_CONFIG_REALM.

Besides, the prefix "KVM_CAP_" in those definitions, except the first 5 definitions like
KVM_CAP_ARM_RME_CONFIG_REALM, are confusing. The macros with "KVM_CAP_" prefix are usually
indicating capabilities. In this specific case, they're applied to the argument (struct),
carried by the corresponding sub-command. So I would suggest to eleminate the prefix,
something like below:

/* List of configurations accepted for KVM_CAP_ARM_RME_CONFIG_REALM */
#define ARM_RME_CONFIG_RPV		0
#define ARM_RME_CONFIG_HASH_ALGO	1

#define ARM_RME_CONFIG_MEASUREMENT_ALGO_SHA256	0
#define ARM_RME_CONFIG_MEASUREMENT_ALGO_SHA512	1

#define ARM_RME_CONFIG_RPV_SIZE	64

struct arm_rme_config {
         :
};


> +struct kvm_cap_arm_rme_config_item {
> +	__u32 cfg;
> +	union {
> +		/* cfg == KVM_CAP_ARM_RME_CFG_RPV */
> +		struct {
> +			__u8	rpv[KVM_CAP_ARM_RME_RPV_SIZE];
> +		};
> +
> +		/* cfg == KVM_CAP_ARM_RME_CFG_HASH_ALGO */
> +		struct {
> +			__u32	hash_algo;
> +		};
> +
> +		/* Fix the size of the union */
> +		__u8	reserved[256];
> +	};
> +};
> +
> +#define KVM_ARM_RME_POPULATE_FLAGS_MEASURE	BIT(0)
> +struct kvm_cap_arm_rme_populate_realm_args {
> +	__u64 populate_ipa_base;
> +	__u64 populate_ipa_size;
> +	__u32 flags;
> +	__u32 reserved[3];
> +};
> +

BIT(0) has type of 'unsigned long', inconsistent to '__u32 flags'. So it would
be something like below.

#define ARM_RME_POPULATE_REALM_IPA_FLAG_MEASURE		(1 << 0)
struct arm_rme_populate_realm_ipa {
	__u64 base;
	__u64 size;
	__u32 flags;
	__u32 reserved[3];
};

> +struct kvm_cap_arm_rme_init_ipa_args {
> +	__u64 init_ipa_base;
> +	__u64 init_ipa_size;
> +	__u32 reserved[4];
> +};
> +

Similiarly, it would be something like below:

struct arm_rme_init_realm_ipa {
	__u64 base;
	__u64 size;
	__u64 reserved[2];
};

>   /* Device Control API on vcpu fd */
>   #define KVM_ARM_VCPU_PMU_V3_CTRL	0
>   #define   KVM_ARM_VCPU_PMU_V3_IRQ	0
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 502ea63b5d2e..f448198838cf 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -934,6 +934,8 @@ struct kvm_enable_cap {
>   #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
>   #define KVM_CAP_X86_GUEST_MODE 238
>   
> +#define KVM_CAP_ARM_RME 300 /* FIXME: Large number to prevent conflicts */
> +
>   struct kvm_irq_routing_irqchip {
>   	__u32 irqchip;
>   	__u32 pin;
> @@ -1581,4 +1583,14 @@ struct kvm_pre_fault_memory {
>   	__u64 padding[5];
>   };
>   
> +/* Available with KVM_CAP_ARM_RME, only for VMs with KVM_VM_TYPE_ARM_REALM  */
> +struct kvm_arm_rmm_psci_complete {
> +	__u64 target_mpidr;
> +	__u32 psci_status;
> +	__u32 padding[3];
> +};
> +
> +/* FIXME: Update nr (0xd2) when merging */
> +#define KVM_ARM_VCPU_RMM_PSCI_COMPLETE	_IOW(KVMIO, 0xd2, struct kvm_arm_rmm_psci_complete)
> +
>   #endif /* __LINUX_KVM_H */

Thanks,
Gavin