Re: [PATCH v8 06/43] arm64: RME: Define the user ABI

[Gavin Shan <gshan@redhat.com>]

On 4/16/25 11:41 PM, 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 since v7:
>   * Add documentation of new ioctls
>   * Bump the magic numbers to avoid conflicts
> Changes since v6:
>   * Rename some of the symbols to make their usage clearer and avoid
>     repetition.
> 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    | 70 +++++++++++++++++++++++++++++++
>   arch/arm64/include/uapi/asm/kvm.h | 49 ++++++++++++++++++++++
>   include/uapi/linux/kvm.h          | 10 +++++
>   3 files changed, 129 insertions(+)
> 

With below comment addressed:

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 1f8625b7646a..99ba6c82cf37 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -3527,6 +3527,11 @@ Possible features:
>   	      - the KVM_REG_ARM64_SVE_VLS pseudo-register is immutable, and can
>   	        no longer be written using KVM_SET_ONE_REG.
>   
> +	- KVM_ARM_VCPU_REC: Allocate a REC (Realm Execution Context) for this
> +	  VCPU. This must be specified on all VCPUs created in a Realm VM.
> +	  Depends on KVM_CAP_ARM_RME.
> +	  Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_REC).
> +
>   4.83 KVM_ARM_PREFERRED_TARGET
>   -----------------------------
>   
> @@ -5098,6 +5103,7 @@ 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.
> @@ -6452,6 +6458,30 @@ the capability to be present.
>   
>   `flags` must currently be zero.
>   
> +4.144 KVM_ARM_VCPU_RMM_PSCI_COMPLETE
> +------------------------------------
> +
> +:Capability: KVM_CAP_ARM_RME
> +:Architectures: arm64
> +:Type: vcpu ioctl
> +:Parameters: struct kvm_arm_rmm_psci_complete (in)
> +:Returns: 0 if successful, < 0 on error
> +
> +::
> +
> +  struct kvm_arm_rmm_psci_complete {
> +	__u64 target_mpidr;
> +	__u32 psci_status;
> +	__u32 padding[3];
> +  };
> +
> +Where PSCI functions are handled by user space, the RMM needs to be informed of
> +the target of the operation using `target_mpidr`, along with the status
> +(`psci_status`). The RMM v1.0 specification defines two functions that require
> +this call: PSCI_CPU_ON and PSCI_AFFINITY_INFO.
> +
> +If the kernel is handling PSCI then this is done automatically and the VMM
> +doesn't need to call this ioctl.
>   
>   .. _kvm_run:
>   
> @@ -8280,6 +8310,46 @@ aforementioned registers before the first KVM_RUN. These registers are VM
>   scoped, meaning that the same set of values are presented on all vCPUs in a
>   given VM.
>   
> +7.38 KVM_CAP_ARM_RME
> +--------------------
> +
> +:Architectures: arm64
> +:Target: VM
> +:Parameters: args[0] provides an action, args[1] points to a structure in
> +	     memory for some actions.
> +:Returns: 0 on success, negative value on error
> +
> +Used to configure and set up the memory for a Realm. The available actions are:
> +
> +================================= =============================================
> + KVM_CAP_ARM_RME_CONFIG_REALM     Takes struct arm_rme_config as args[1] and
> +                                  configures realm parameters prior to it being
> +                                  created.
> +
> +                                  Options are ARM_RME_CONFIG_RPV to set the
> +                                  "Realm Personalization Value" and
> +                                  ARM_RME_CONFIG_HASH_ALGO to set the hash
> +                                  algorithm.
> +
> + KVM_CAP_ARM_RME_CREATE_REALM     Request the RMM create the realm. The realm's
> +                                  configuration parameters must be set first.
> +
> + KVM_CAP_ARM_RME_INIT_RIPAS_REALM Takes struct arm_rme_init_ripas as args[1]
> +                                  and sets the RIPAS (Realm IPA State) to
> +                                  RIPAS_RAM of a specified area of the realm's
> +                                  IPA.
> +
> + KVM_CAP_ARM_RME_POPULATE_REALM   Takes struct arm_rme_init_ripas as args[1]
> +                                  and populates a region of protected address
> +                                  space by copying the data from the shared
> +                                  alias.
> +
> + KVM_CAP_ARM_RME_ACTIVATE_REALM   Request the RMM activate the realm. No
> +                                  further changes can be made to the realm's
> +                                  configuration, and VCPUs are not permitted to
> +                                  enter the realm until it has been activated.
                                                               ^^^^^^^^^^^^^^^^^^
s/has been activated/is deactivated

I don't see where the guard is applied to prevent vCPU is added after realm
has been activated. I may missed that. Otherwise, it's something to be improved
n the subsequent patch where a vCPU is created and added to the realm.


> +================================= =============================================
> +
>   8. Other capabilities.
>   ======================
>   
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index af9d9acaf997..b57712880605 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -106,6 +106,7 @@ struct kvm_regs {
>   #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_HAS_EL2_E2H0	8 /* Limit NV support to E2H RES0 */
> +#define KVM_ARM_VCPU_REC		9 /* VCPU REC state as part of Realm */
>   
>   struct kvm_vcpu_init {
>   	__u32 target;
> @@ -429,6 +430,54 @@ 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_REALM		1
> +#define KVM_CAP_ARM_RME_INIT_RIPAS_REALM	2
> +#define KVM_CAP_ARM_RME_POPULATE_REALM		3
> +#define KVM_CAP_ARM_RME_ACTIVATE_REALM		4
> +
> +/* List of configuration items 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 {
> +	__u32 cfg;
> +	union {
> +		/* cfg == ARM_RME_CONFIG_RPV */
> +		struct {
> +			__u8	rpv[ARM_RME_CONFIG_RPV_SIZE];
> +		};
> +
> +		/* cfg == ARM_RME_CONFIG_HASH_ALGO */
> +		struct {
> +			__u32	hash_algo;
> +		};
> +
> +		/* Fix the size of the union */
> +		__u8	reserved[256];
> +	};
> +};
> +
> +#define KVM_ARM_RME_POPULATE_FLAGS_MEASURE	(1 << 0)
> +struct arm_rme_populate_realm {
> +	__u64 base;
> +	__u64 size;
> +	__u32 flags;
> +	__u32 reserved[3];
> +};
> +
> +struct arm_rme_init_ripas {
> +	__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 b6ae8ad8934b..0b8479985581 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -930,6 +930,7 @@ struct kvm_enable_cap {
>   #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
>   #define KVM_CAP_X86_GUEST_MODE 238
>   #define KVM_CAP_ARM_WRITABLE_IMP_ID_REGS 239
> +#define KVM_CAP_ARM_RME 240
>   
>   struct kvm_irq_routing_irqchip {
>   	__u32 irqchip;
> @@ -1582,4 +1583,13 @@ 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];
> +};
> +
> +#define KVM_ARM_VCPU_RMM_PSCI_COMPLETE	_IOW(KVMIO, 0xd6, struct kvm_arm_rmm_psci_complete)
> +
>   #endif /* __LINUX_KVM_H */

Thanks,
Gavin