Re: [PATCH v22 18/23] KVM: arm64: CCA: Introduce Realms
From: Suzuki K Poulose
Date: Tue Oct 06 2026 - 01:11:33 EST
On 06/10/2026 04:42, Gavin Shan wrote:
On 10/5/26 7:07 PM, Suzuki K Poulose wrote:
From: Steven Price <steven.price@xxxxxxx>
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.
Please note that we cannot create Realm VMs yet. This requires further
changes to the UABI and core RMI driver support, which will come later.
Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxxxxxxxx>
Signed-off-by: Steven Price <steven.price@xxxxxxx>
Co-developed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
arch/arm64/include/asm/kvm_emulate.h | 16 ++++++++
arch/arm64/include/asm/kvm_host.h | 19 ++++++---
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 | 6 +++
arch/arm64/kvm/mmu.c | 1 +
arch/arm64/kvm/rmi.c | 18 ++++++++
8 files changed, 118 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 dfa9d4ec61a76..3debffef638a4 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
@@ -334,6 +335,7 @@ enum kvm_arm_vm_flavor {
VM_PKVM, /* Normal guests on pKVM */
MARKER(__VM_PROTECTED),
VM_PROTECTED_PKVM, /* Protected VM */
+ VM_REALM, /* CCA */
VM_FLAVOR_MAX
};
@@ -450,11 +452,14 @@ 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 */
@@ -1565,6 +1570,10 @@ struct kvm *kvm_arch_alloc_vm(void);
(__kvm && kvm_vm_is_protected_pkvm(__kvm)); \
})
+
+#define kvm_vm_is_realm(kvm) ((kvm)->arch.vm_flavor == VM_REALM)
+#define vcpu_is_rec(vcpu) kvm_vm_is_realm((vcpu)->kvm)
+
vcpu_is_rec() isn't safely called in nVHE hyp stub. So do we need add something
similiar to what we had for vcpu_is_protected(vcpu) in PATCH[05]?
#ifdef __KVM_NVHE_HYPERVISOR__
/* vcpu_is_rec() isn't expected to called in nVHE hyp stub */
#define vcpu_is_rec(vcpu) BUILD_BUG_ON(1)
#else
#define vcpu_is_rec(vcpu) kvm_vm_is_realm((vcpu)->kvm)
#endif
#define kvm_vm_hyp_is_distrusting(kvm) ((kvm)->arch.vm_flavor >= __VM_DISTRUSTING_HYP)^^^^^
int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature);
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.
Granule instead of page is the term applicable to RMM. Lets use a generic
term 'memory' here. Also, lets mention the name of the function used to
populate the memory (granules), which is consistent to the comments for
REALM_STATE_ACTIVE.
Memory may be populated by rmi_rtt_data_map_init().
+ */
+ 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,
rmi_data_create() is an invalid function name.
Memory can't longer be populated using rmi_rtt_data_map_init().
Ack, thanks for spotting, I will fix them.
Cheers
Suzuki