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Message-ID: <60e5f88e-c8f1-40d9-a69c-e7da4fc1c953@redhat.com>
Date: Tue, 1 Jul 2025 16:29:03 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
kvmarm@...ts.linux.dev
Cc: Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
Oliver Upton <oliver.upton@...ux.dev>,
Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu
<yuzenghui@...wei.com>, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, Joey Gouly <joey.gouly@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Christoffer Dall <christoffer.dall@....com>, Fuad Tabba <tabba@...gle.com>,
linux-coco@...ts.linux.dev,
Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
<alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
Emi Kisanuki <fj0570is@...itsu.com>
Subject: Re: [PATCH v9 06/43] arm64: RME: Define the user ABI
On 6/11/25 8:48 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@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> Changes since v8:
> * Minor improvements to documentation following review.
> * Bump the magic numbers to avoid conflicts.
> 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 | 73 ++++++++++++++++++++++++++++++-
> arch/arm64/include/uapi/asm/kvm.h | 49 +++++++++++++++++++++
> include/uapi/linux/kvm.h | 10 +++++
> 3 files changed, 131 insertions(+), 1 deletion(-)
>
With below nitpicks addressed:
Reviewed-by: Gavin Shan <gshan@...hat.com>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 1bd2d42e6424..65543289f75c 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -3542,6 +3542,11 @@ Possible features:
> Depends on KVM_CAP_ARM_EL2_E2H0.
> KVM_ARM_VCPU_HAS_EL2 must also be set.
>
> + - 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
> -----------------------------
>
> @@ -5115,6 +5120,7 @@ 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.
> @@ -6469,6 +6475,30 @@ 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:
>
> @@ -8528,7 +8558,7 @@ ENOSYS for the others.
> When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of
> type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request.
>
> -7.37 KVM_CAP_ARM_WRITABLE_IMP_ID_REGS
> +7.42 KVM_CAP_ARM_WRITABLE_IMP_ID_REGS
> -------------------------------------
>
> :Architectures: arm64
> @@ -8557,6 +8587,47 @@ given VM.
> When this capability is enabled, KVM resets the VCPU when setting
> MP_STATE_INIT_RECEIVED through IOCTL. The original MP_STATE is preserved.
>
> +7.44 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.
^^^
Alignment
s/for some actions/for the action
> +: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 to 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_populate_realm 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 to activate the realm. No
> + changes can be made to the Realm's memory,
> + IPA state or configuration parameters. No
> + new VCPUs should be created after this step.
> +================================= =============================================
> +
The description about KVM_CAP_ARM_RME_ACTIVATE_REALM looks a bit confusing, maybe
something as below is more clear:
KVM_CAP_ARM_RME_ACTIVATE_REALM Request the RMM to activate the realm. No changes
can be made to the Realm's populated memory, IPA state,
configuration parameters or vCPU addition after this
step.
> 8. Other capabilities.
> ======================
>
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index ed5f3892674c..9b5d67ecbc5e 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_HASH_ALGO_SHA256 0
> +#define ARM_RME_CONFIG_HASH_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 d00b85cb168c..3690664e272c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -934,6 +934,7 @@ struct kvm_enable_cap {
> #define KVM_CAP_ARM_EL2 240
> #define KVM_CAP_ARM_EL2_E2H0 241
> #define KVM_CAP_RISCV_MP_STATE_RESET 242
> +#define KVM_CAP_ARM_RME 243
>
> struct kvm_irq_routing_irqchip {
> __u32 irqchip;
> @@ -1586,4 +1587,13 @@ 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
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