[PATCH v14 11/44] arm64: RMI: Check for RMI support at KVM init
Steven Price
steven.price at arm.com
Wed May 13 06:17:19 PDT 2026
Check if the RMI support is sufficient for using in KVM. Specifically we
currently only support KVM in VHE mode when for creating realm VMs.
Signed-off-by: Steven Price <steven.price at arm.com>
---
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_host.h | 4 ++++
arch/arm64/include/asm/kvm_rmi.h | 17 +++++++++++++++++
arch/arm64/include/asm/virt.h | 1 +
arch/arm64/kvm/Makefile | 2 +-
arch/arm64/kvm/arm.c | 5 +++++
arch/arm64/kvm/rmi.c | 24 ++++++++++++++++++++++++
6 files changed, 52 insertions(+), 1 deletion(-)
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_host.h b/arch/arm64/include/asm/kvm_host.h
index 851f6171751c..3512696ed506 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
@@ -424,6 +425,9 @@ struct kvm_arch {
/* Nested virtualization info */
struct dentry *debugfs_nv_dentry;
#endif
+
+ bool is_realm;
+ struct realm realm;
};
struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
new file mode 100644
index 000000000000..4936007947fd
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023-2025 ARM Ltd.
+ */
+
+#ifndef __ASM_KVM_RMI_H
+#define __ASM_KVM_RMI_H
+
+/**
+ * struct realm - Additional per VM data for a Realm
+ */
+struct realm {
+};
+
+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 b546703c3ab9..92cec42952f4 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 59612d2f277c..ed3cf30eb06e 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 176cbe8baad3..247e03b33035 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -41,6 +41,7 @@
#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>
@@ -109,6 +110,8 @@ 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);
@@ -2975,6 +2978,8 @@ 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 000000000000..1acc972a4b92
--- /dev/null
+++ b/arch/arm64/kvm/rmi.c
@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023-2025 ARM Ltd.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/rmi_cmds.h>
+#include <asm/virt.h>
+
+void kvm_init_rmi(void)
+{
+ /*
+ * TODO: Support Realm guests in nVHE mode, this will require adding
+ * EL2 stub(s) for REC entry and possibly other things.
+ */
+ if (!is_kernel_in_hyp_mode())
+ return;
+
+ if (!rmi_is_available())
+ return;
+
+ /* Future patch will enable static branch kvm_rmi_is_available */
+}
--
2.43.0
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