[PATCH v17 07/20] KVM: arm64: CCA: Introduce Realms
Suzuki K Poulose
suzuki.poulose at arm.com
Tue Sep 8 09:22:10 PDT 2026
From: Steven Price <steven.price at arm.com>
Add foundational work for supporting Realms.
- Add a new VM flavor.
- At KVM init, check if the KVM can support Realms (though not functional yet)
and will be advertised by static key kvm_rmi_is_available. This will be
turned on in a later patches, once we have all the bits and pieces ready.
For now check if we are blessed with KVM_MODE_RMM.
- Add realm specific tracking in kvm_arch. Since Realm and protected pKVM
states are mutually exclusive, move them into a union.
Signed-off-by: Steven Price <steven.price at arm.com>
Co-Developed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
---
Changes since v16:
* Share mutually exclusive pKVM and Realm per-VM storage in a union.
* Move to the new VM flavor infrastructure, split bits out. Trimmed down
* Move in Realm state and basic boiler plates
Changes since v13:
* Most of the init has been moved out of the 'kvm' directory so this is
much more basic now.
Changes since v12:
* Drop check for 4k page size.
Changes since v11:
* Reword slightly the comments on the realm states.
Changes since v10:
* kvm_is_realm() no longer has a NULL check.
* Rename from "rme" to "rmi" when referring to the RMM interface.
* Check for RME (hardware) support before probing for RMI support.
Changes since v8:
* No need to guard kvm_init_rme() behind 'in_hyp_mode'.
Changes since v6:
* Improved message for an unsupported RMI ABI version.
Changes since v5:
* Reword "unsupported" message from "host supports" to "we want" to
clarify that 'we' are the 'host'.
Changes since v2:
* Drop return value from kvm_init_rme(), it was always 0.
* Rely on the RMM return value to identify whether the RSI ABI is
compatible.
---
arch/arm64/include/asm/kvm_emulate.h | 16 ++++++++
arch/arm64/include/asm/kvm_host.h | 17 +++++---
arch/arm64/include/asm/kvm_rmi.h | 61 ++++++++++++++++++++++++++++
arch/arm64/include/asm/virt.h | 1 +
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/arm.c | 5 +++
arch/arm64/kvm/rmi.c | 18 ++++++++
7 files changed, 114 insertions(+), 6 deletions(-)
create mode 100644 arch/arm64/include/asm/kvm_rmi.h
create mode 100644 arch/arm64/kvm/rmi.c
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index a3c1928bdf743..d360a8b05b8bf 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -793,4 +793,20 @@ static inline void kvm_reset_vcpu_psci(struct kvm_vcpu *vcpu,
vcpu_set_reg(vcpu, 0, reset_state->r0);
}
+static inline enum realm_state kvm_realm_state(struct kvm *kvm)
+{
+ return READ_ONCE(kvm->arch.realm.state);
+}
+
+static inline void kvm_set_realm_state(struct kvm *kvm,
+ enum realm_state new_state)
+{
+ WRITE_ONCE(kvm->arch.realm.state, new_state);
+}
+
+static inline bool kvm_realm_is_created(struct kvm *kvm)
+{
+ return kvm_vm_is_realm(kvm) && kvm_realm_state(kvm) != REALM_STATE_NONE;
+}
+
#endif /* __ARM64_KVM_EMULATE_H__ */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 31ae9d8d8e92f..824a3383409c8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -27,6 +27,7 @@
#include <asm/fpsimd.h>
#include <asm/kvm.h>
#include <asm/kvm_asm.h>
+#include <asm/kvm_rmi.h>
#include <asm/vncr_mapping.h>
#define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -316,6 +317,7 @@ enum kvm_arm_vm_flavor {
VM_VHE,
VM_PKVM, /* Normal guests on PKVM */
VM_PROTECTED_PKVM, /* Protected VM */
+ VM_REALM, /* CCA */
VM_FLAVOR_MAX,
};
@@ -431,11 +433,14 @@ struct kvm_arch {
/* Count the number of VNCR_EL2 TLBs */
atomic_t vncr_tlb_count;
- /*
- * For an untrusted host VM, 'pkvm.handle' is used to lookup
- * the associated pKVM instance in the hypervisor.
- */
- struct kvm_protected_vm pkvm;
+ union {
+ /*
+ * For an untrusted host VM, 'pkvm.handle' is used to lookup
+ * the associated pKVM instance in the hypervisor.
+ */
+ struct kvm_protected_vm pkvm;
+ struct realm realm;
+ };
#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
/* Nested virtualization info */
@@ -1520,8 +1525,10 @@ struct kvm *kvm_arch_alloc_vm(void);
#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
#define kvm_vm_is_protected(kvm) ((kvm)->arch.vm_flavor == VM_PROTECTED_PKVM)
+#define kvm_vm_is_realm(kvm) ((kvm)->arch.vm_flavor == VM_REALM)
#define vcpu_is_protected(vcpu) kvm_vm_is_protected((vcpu)->kvm)
+#define vcpu_is_rec(vcpu) kvm_vm_is_realm((vcpu)->kvm)
int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
new file mode 100644
index 0000000000000..44f5c75a27b5b
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023-2026 ARM Ltd.
+ */
+
+#ifndef __ASM_KVM_RMI_H
+#define __ASM_KVM_RMI_H
+
+/**
+ * enum realm_state - State of a Realm
+ *
+ * Mirrors the RMM's Realm lifecycle states where they are meaningful to KVM,
+ * with REALM_STATE_DYING being a KVM-internal state used to prevent further
+ * requests while teardown is in progress. KVM does not track REALM_SYSTEM_OFF
+ * or REALM_ZOMBIE separately as they naturally lead to teardown.
+ */
+enum realm_state {
+ /**
+ * @REALM_STATE_NONE:
+ * Realm has not yet been created. rmi_realm_create() has not
+ * yet been called.
+ */
+ REALM_STATE_NONE,
+ /**
+ * @REALM_STATE_NEW:
+ * Realm is under construction, rmi_realm_create() has been
+ * called, but it is not yet activated. Pages may be populated.
+ */
+ REALM_STATE_NEW,
+ /**
+ * @REALM_STATE_ACTIVE:
+ * Realm has been created and is eligible for execution with
+ * rmi_rec_enter(). Pages may no longer be populated with
+ * rmi_data_create().
+ */
+ REALM_STATE_ACTIVE,
+ /**
+ * @REALM_STATE_DYING:
+ * Realm is in the process of being destroyed or has already been
+ * destroyed.
+ */
+ REALM_STATE_DYING,
+ /**
+ * @REALM_STATE_DEAD:
+ * Realm has been destroyed.
+ */
+ REALM_STATE_DEAD
+};
+
+/**
+ * struct realm - Additional per VM data for a Realm
+ *
+ * @state: The lifetime state machine for the realm
+ */
+struct realm {
+ enum realm_state state;
+};
+
+void kvm_init_rmi(void);
+
+#endif /* __ASM_KVM_RMI_H */
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index b546703c3ab9a..92cec42952f42 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -87,6 +87,7 @@ void __hyp_reset_vectors(void);
bool is_kvm_arm_initialised(void);
DECLARE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
+DECLARE_STATIC_KEY_FALSE(kvm_rmi_is_available);
static inline bool is_pkvm_initialized(void)
{
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 59612d2f277c1..ed3cf30eb06e7 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -16,7 +16,7 @@ CFLAGS_handle_exit.o += -Wno-override-init
kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
inject_fault.o va_layout.o handle_exit.o config.o \
guest.o debug.o reset.o sys_regs.o stacktrace.o \
- vgic-sys-reg-v3.o fpsimd.o pkvm.o \
+ vgic-sys-reg-v3.o fpsimd.o pkvm.o rmi.o \
arch_timer.o trng.o vmid.o emulate-nested.o nested.o at.o \
vgic/vgic.o vgic/vgic-init.o \
vgic/vgic-irqfd.o vgic/vgic-v2.o \
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 50f0adfadab38..2ecd92156f7cc 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -42,6 +42,7 @@
#include <asm/kvm_nested.h>
#include <asm/kvm_pkvm.h>
#include <asm/kvm_ptrauth.h>
+#include <asm/kvm_rmi.h>
#include <asm/sections.h>
#include <asm/stacktrace/nvhe.h>
@@ -113,6 +114,8 @@ long kvm_get_cap_for_kvm_ioctl(unsigned int ioctl, long *ext)
return -EINVAL;
}
+DEFINE_STATIC_KEY_FALSE(kvm_rmi_is_available);
+
DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_base);
@@ -3159,6 +3162,8 @@ static __init int kvm_arm_init(void)
in_hyp_mode = is_kernel_in_hyp_mode();
+ kvm_init_rmi();
+
if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) ||
cpus_have_final_cap(ARM64_WORKAROUND_1508412))
kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
new file mode 100644
index 0000000000000..5ecc8b3498698
--- /dev/null
+++ b/arch/arm64/kvm/rmi.c
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023-2026 ARM Ltd.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/virt.h>
+
+void kvm_init_rmi(void)
+{
+ if (kvm_get_mode() != KVM_MODE_RMM)
+ return;
+
+ /* TODO: Check if the RMI is available */
+
+ /* Future patch will enable static branch kvm_rmi_is_available */
+}
--
2.43.0
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