[PATCH v7 06/45] arm64: RME: Check for RME support at KVM init

Steven Price
2025-02-13T16:15:11Z

Query the RMI version number and check if it is a compatible version. A
static key is also provided to signal that a supported RMM is available.

Functions are provided to query if a VM or VCPU is a realm (or rec)
which currently will always return false.

Signed-off-by: Steven Price <steven.price@arm.com>
---
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 | 18 +++++++++
arch/arm64/include/asm/kvm_host.h | 4 ++
arch/arm64/include/asm/kvm_rme.h | 56 ++++++++++++++++++++++++++++
arch/arm64/include/asm/virt.h | 1 +
arch/arm64/kvm/Makefile | 3 +-
arch/arm64/kvm/arm.c | 6 +++
arch/arm64/kvm/rme.c | 56 ++++++++++++++++++++++++++++
7 files changed, 143 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/include/asm/kvm_rme.h
create mode 100644 arch/arm64/kvm/rme.c

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 47f2cf408eed..52c7a8923c65 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -691,4 +691,22 @@ static inline bool guest_hyp_sve_traps_enabled(const struct kvm_vcpu *vcpu)
{
return __guest_hyp_cptr_xen_trap_enabled(vcpu, ZEN);
}
+
+static inline bool kvm_is_realm(struct kvm *kvm)
+{
+ if (static_branch_unlikely(&kvm_rme_is_available) && kvm)
+ return kvm->arch.is_realm;
+ return false;
+}
+
+static inline enum realm_state kvm_realm_state(struct kvm *kvm)
+{
+ return READ_ONCE(kvm->arch.realm.state);
+}
+
+static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu)
+{
+ return false;
+}
+
#endif /* __ARM64_KVM_EMULATE_H__ */
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7cfa024de4e3..992eb2a6f56f 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_rme.h>
#include <asm/vncr_mapping.h>

#define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -383,6 +384,9 @@ struct kvm_arch {
* the associated pKVM instance in the hypervisor.
*/
struct kvm_protected_vm pkvm;
+
+ bool is_realm;
+ struct realm realm;
};

struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
new file mode 100644
index 000000000000..69af5c3a1e44
--- /dev/null
+++ b/arch/arm64/include/asm/kvm_rme.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+
+#ifndef __ASM_KVM_RME_H
+#define __ASM_KVM_RME_H
+
+/**
+ * enum realm_state - State of a Realm
+ */
+enum realm_state {
+ /**
+ * @REALM_STATE_NONE:
+ * Realm has not yet been created. rmi_realm_create() may be
+ * called to create the realm.
+ */
+ REALM_STATE_NONE,
+ /**
+ * @REALM_STATE_NEW:
+ * Realm is under construction, not eligible for execution. Pages
+ * may be populated with rmi_data_create().
+ */
+ 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_rme(void);
+
+#endif
diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index ebf4a9f943ed..e45d47156dcf 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -81,6 +81,7 @@ void __hyp_reset_vectors(void);
bool is_kvm_arm_initialised(void);

DECLARE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
+DECLARE_STATIC_KEY_FALSE(kvm_rme_is_available);

static inline bool is_pkvm_initialized(void)
{
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 3cf7adb2b503..ce8a10d3161d 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -23,7 +23,8 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
vgic/vgic-v3.o vgic/vgic-v4.o \
vgic/vgic-mmio.o vgic/vgic-mmio-v2.o \
vgic/vgic-mmio-v3.o vgic/vgic-kvm-device.o \
- vgic/vgic-its.o vgic/vgic-debug.o
+ vgic/vgic-its.o vgic/vgic-debug.o \
+ rme.o

kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o
kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 646e806c6ca6..6d371a2b648a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -40,6 +40,7 @@
#include <asm/kvm_nested.h>
#include <asm/kvm_pkvm.h>
#include <asm/kvm_ptrauth.h>
+#include <asm/kvm_rme.h>
#include <asm/sections.h>

#include <kvm/arm_hypercalls.h>
@@ -59,6 +60,8 @@ enum kvm_wfx_trap_policy {
static enum kvm_wfx_trap_policy kvm_wfi_trap_policy __read_mostly = KVM_WFX_NOTRAP_SINGLE_TASK;
static enum kvm_wfx_trap_policy kvm_wfe_trap_policy __read_mostly = KVM_WFX_NOTRAP_SINGLE_TASK;

+DEFINE_STATIC_KEY_FALSE(kvm_rme_is_available);
+
DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);

DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_base);
@@ -2759,6 +2762,9 @@ static __init int kvm_arm_init(void)

in_hyp_mode = is_kernel_in_hyp_mode();

+ if (in_hyp_mode)
+ kvm_init_rme();
+
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/rme.c b/arch/arm64/kvm/rme.c
new file mode 100644
index 000000000000..67cf2d94cb2d
--- /dev/null
+++ b/arch/arm64/kvm/rme.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 ARM Ltd.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <asm/rmi_cmds.h>
+#include <asm/virt.h>
+
+static int rmi_check_version(void)
+{
+ struct arm_smccc_res res;
+ unsigned short version_major, version_minor;
+ unsigned long host_version = RMI_ABI_VERSION(RMI_ABI_MAJOR_VERSION,
+ RMI_ABI_MINOR_VERSION);
+
+ arm_smccc_1_1_invoke(SMC_RMI_VERSION, host_version, &res);
+
+ if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
+ return -ENXIO;
+
+ version_major = RMI_ABI_VERSION_GET_MAJOR(res.a1);
+ version_minor = RMI_ABI_VERSION_GET_MINOR(res.a1);
+
+ if (res.a0 != RMI_SUCCESS) {
+ unsigned short high_version_major, high_version_minor;
+
+ high_version_major = RMI_ABI_VERSION_GET_MAJOR(res.a2);
+ high_version_minor = RMI_ABI_VERSION_GET_MINOR(res.a2);
+
+ kvm_err("Unsupported RMI ABI (v%d.%d - v%d.%d) we want v%d.%d\n",
+ version_major, version_minor,
+ high_version_major, high_version_minor,
+ RMI_ABI_MAJOR_VERSION,
+ RMI_ABI_MINOR_VERSION);
+ return -ENXIO;
+ }
+
+ kvm_info("RMI ABI version %d.%d\n", version_major, version_minor);
+
+ return 0;
+}
+
+void kvm_init_rme(void)
+{
+ if (PAGE_SIZE != SZ_4K)
+ /* Only 4k page size on the host is supported */
+ return;
+
+ if (rmi_check_version())
+ /* Continue without realm support */
+ return;
+
+ /* Future patch will enable static branch kvm_rme_is_available */
+}
--
2.43.0