[PATCH v14 06/44] arm64: RMI: Check for RMI support at init

[Steven Price]

Query the RMI version number and check if it is a compatible version.
The first two feature registers are read and exposed for future code to
use.

Signed-off-by: Steven Price <steven.price at arm.com>
---
v14:
 * This moves the basic RMI setup into the 'kernel' directory. This is
   because RMI will be used for some features outside of KVM so should
   be available even if KVM isn't compiled in.
---
 arch/arm64/include/asm/rmi_cmds.h |  3 ++
 arch/arm64/kernel/Makefile        |  2 +-
 arch/arm64/kernel/cpufeature.c    |  1 +
 arch/arm64/kernel/rmi.c           | 65 +++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/kernel/rmi.c

diff --git a/arch/arm64/include/asm/rmi_cmds.h b/arch/arm64/include/asm/rmi_cmds.h
index 04f7066894e9..9179934925c5 100644
--- a/arch/arm64/include/asm/rmi_cmds.h
+++ b/arch/arm64/include/asm/rmi_cmds.h
@@ -10,6 +10,9 @@
 
 #include <asm/rmi_smc.h>
 
+extern unsigned long rmm_feat_reg0;
+extern unsigned long rmm_feat_reg1;
+
 struct rtt_entry {
 	unsigned long walk_level;
 	unsigned long desc;
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 74b76bb70452..d68f351aae75 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -34,7 +34,7 @@ obj-y			:= debug-monitors.o entry.o irq.o fpsimd.o		\
 			   cpufeature.o alternative.o cacheinfo.o		\
 			   smp.o smp_spin_table.o topology.o smccc-call.o	\
 			   syscall.o proton-pack.o idle.o patching.o pi/	\
-			   rsi.o jump_label.o
+			   rsi.o jump_label.o rmi.o
 
 obj-$(CONFIG_COMPAT)			+= sys32.o signal32.o			\
 					   sys_compat.o
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6d53bb15cf7b..8bdd95a8c2de 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -292,6 +292,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar3[] = {
 static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV3_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV2_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_RME_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_DIT_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_AMU_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_MPAM_SHIFT, 4, 0),
diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c
new file mode 100644
index 000000000000..99c1ccc35c11
--- /dev/null
+++ b/arch/arm64/kernel/rmi.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023-2025 ARM Ltd.
+ */
+
+#include <linux/memblock.h>
+
+#include <asm/rmi_cmds.h>
+
+unsigned long rmm_feat_reg0;
+unsigned long rmm_feat_reg1;
+
+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);
+	unsigned long aa64pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
+
+	/* If RME isn't supported, then RMI can't be */
+	if (cpuid_feature_extract_unsigned_field(aa64pfr0, ID_AA64PFR0_EL1_RME_SHIFT) == 0)
+		return -ENXIO;
+
+	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);
+
+		pr_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;
+	}
+
+	pr_info("RMI ABI version %d.%d\n", version_major, version_minor);
+
+	return 0;
+}
+
+static int __init arm64_init_rmi(void)
+{
+	/* Continue without realm support if we can't agree on a version */
+	if (rmi_check_version())
+		return 0;
+
+	if (WARN_ON(rmi_features(0, &rmm_feat_reg0)))
+		return 0;
+	if (WARN_ON(rmi_features(1, &rmm_feat_reg1)))
+		return 0;
+
+	return 0;
+}
+subsys_initcall(arm64_init_rmi);
-- 
2.43.0