feat(cpufeat): enable FEAT_SME for FEAT_STATE_CHECKED

Add support for runtime detection (ENABLE_SME_FOR_NS=2), by splitting
feat_sme_supported() into an ID register reading function and a
second function to report the support status. That function considers
both build time settings and runtime information (if needed), and is
used before we do SME specific setup.

Change the FVP platform default to the now supported dynamic option
(=2),so the right decision can be made by the code at runtime.

Change-Id: Ida9ccf737db5be20865b84f42b1f9587be0626ab
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>

13 files changed, 83 insertions, 41 deletions

diff --git a/Makefile b/Makefile
index 52d6cf576..20b2aa296 100644
--- a/Makefile
+++ b/Makefile
@@ -861,6 +861,10 @@ ifeq ($(FEATURE_DETECTION),1)
     $(info FEATURE_DETECTION is an experimental feature)
 endif
 
+ifneq ($(ENABLE_SME_FOR_NS), 0)
+    $(info ENABLE_SME_FOR_NS is an experimental feature)
+endif
+
 ifeq (${ARM_XLAT_TABLES_LIB_V1}, 1)
     ifeq (${ALLOW_RO_XLAT_TABLES}, 1)
         $(error "ALLOW_RO_XLAT_TABLES requires translation tables library v2")
@@ -877,7 +881,7 @@ endif
 ifeq (${ARCH},aarch32)
 
     # SME/SVE only supported on AArch64
-    ifeq (${ENABLE_SME_FOR_NS},1)
+    ifneq (${ENABLE_SME_FOR_NS},0)
         $(error "ENABLE_SME_FOR_NS cannot be used with ARCH=aarch32")
     endif
     ifeq (${ENABLE_SVE_FOR_NS},1)
@@ -898,7 +902,7 @@ endif
 
 # Ensure ENABLE_RME is not used with SME
 ifeq (${ENABLE_RME},1)
-    ifeq (${ENABLE_SME_FOR_NS},1)
+    ifneq (${ENABLE_SME_FOR_NS},0)
         $(error "ENABLE_SME_FOR_NS cannot be used with ENABLE_RME")
     endif
 endif
@@ -918,7 +922,7 @@ endif
 # SVE and SME cannot be used with CTX_INCLUDE_FPREGS since secure manager does
 # its own context management including FPU registers.
 ifeq (${CTX_INCLUDE_FPREGS},1)
-    ifeq (${ENABLE_SME_FOR_NS},1)
+    ifneq (${ENABLE_SME_FOR_NS},0)
         $(error "ENABLE_SME_FOR_NS cannot be used with CTX_INCLUDE_FPREGS")
     endif
     ifeq (${ENABLE_SVE_FOR_NS},1)
@@ -1101,7 +1105,6 @@ $(eval $(call assert_booleans,\
         ENABLE_PMF \
         ENABLE_PSCI_STAT \
         ENABLE_RUNTIME_INSTRUMENTATION \
-        ENABLE_SME_FOR_NS \
         ENABLE_SME_FOR_SWD \
         ENABLE_SVE_FOR_NS \
         ENABLE_SVE_FOR_SWD \
@@ -1189,6 +1192,7 @@ $(eval $(call assert_numerics,\
         ENABLE_RME \
         ENABLE_SPE_FOR_NS \
         ENABLE_SYS_REG_TRACE_FOR_NS \
+        ENABLE_SME_FOR_NS \
         ENABLE_TRF_FOR_NS \
         FW_ENC_STATUS \
         NR_OF_FW_BANKS \
diff --git a/bl31/bl31.mk b/bl31/bl31.mk
index bf907eaa5..8f3725ad5 100644
--- a/bl31/bl31.mk
+++ b/bl31/bl31.mk
@@ -99,7 +99,7 @@ ifeq (${ENABLE_MPMM},1)
 BL31_SOURCES		+=	${MPMM_SOURCES}
 endif
 
-ifeq (${ENABLE_SME_FOR_NS},1)
+ifneq (${ENABLE_SME_FOR_NS},0)
 BL31_SOURCES		+=	lib/extensions/sme/sme.c
 BL31_SOURCES		+=	lib/extensions/sve/sve.c
 else
diff --git a/common/feat_detect.c b/common/feat_detect.c
index 12cf12638..609a38888 100644
--- a/common/feat_detect.c
+++ b/common/feat_detect.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2022-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -216,6 +216,8 @@ void detect_arch_features(void)
 		      "TRBE", 1, 1);
 
 	/* v9.2 features */
+	check_feature(ENABLE_SME_FOR_NS, read_feat_sme_id_field(),
+		      "SME", 1, 2);
 	read_feat_rme();
 
 	if (tainted) {
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 20d88071b..4483dd424 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -406,14 +406,15 @@ Common build options
    instrumented. Enabling this option enables the ``ENABLE_PMF`` build option
    as well. Default is 0.
 
--  ``ENABLE_SME_FOR_NS``: Boolean option to enable Scalable Matrix Extension
+-  ``ENABLE_SME_FOR_NS``: Numeric value to enable Scalable Matrix Extension
    (SME), SVE, and FPU/SIMD for the non-secure world only. These features share
    registers so are enabled together. Using this option without
    ENABLE_SME_FOR_SWD=1 will cause SME, SVE, and FPU/SIMD instructions in secure
    world to trap to EL3. SME is an optional architectural feature for AArch64
    and TF-A support is experimental. At this time, this build option cannot be
    used on systems that have SPD=spmd/SPM_MM or ENABLE_RME, and attempting to
-   build with these options will fail. Default is 0.
+   build with these options will fail. This flag can take the values 0 to 2, to
+   align with the ``FEATURE_DETECTION`` mechanism. Default is 0.
 
 -  ``ENABLE_SME_FOR_SWD``: Boolean option to enable the Scalable Matrix
    Extension for secure world use along with SVE and FPU/SIMD, ENABLE_SME_FOR_NS
diff --git a/include/arch/aarch64/arch.h b/include/arch/aarch64/arch.h
index 8663ab8e7..2ce1be8f0 100644
--- a/include/arch/aarch64/arch.h
+++ b/include/arch/aarch64/arch.h
@@ -393,8 +393,10 @@
 #define ID_AA64PFR1_MPAM_FRAC_SHIFT	ULL(16)
 #define ID_AA64PFR1_MPAM_FRAC_MASK	ULL(0xf)
 
-#define ID_AA64PFR1_EL1_SME_SHIFT	U(24)
-#define ID_AA64PFR1_EL1_SME_MASK	ULL(0xf)
+#define ID_AA64PFR1_EL1_SME_SHIFT		U(24)
+#define ID_AA64PFR1_EL1_SME_MASK		ULL(0xf)
+#define ID_AA64PFR1_EL1_SME_NOT_SUPPORTED	ULL(0x0)
+#define ID_AA64PFR1_EL1_SME_SUPPORTED		ULL(0x1)
 
 /* ID_PFR1_EL1 definitions */
 #define ID_PFR1_VIRTEXT_SHIFT	U(12)
@@ -1004,7 +1006,9 @@
 #define SMCR_EL3			S3_6_C1_C2_6
 
 /* ID_AA64SMFR0_EL1 definitions */
-#define ID_AA64SMFR0_EL1_FA64_BIT	(UL(1) << 63)
+#define ID_AA64SMFR0_EL1_SME_FA64_SHIFT		U(63)
+#define ID_AA64SMFR0_EL1_SME_FA64_MASK		U(0x1)
+#define ID_AA64SMFR0_EL1_SME_FA64_SUPPORTED	U(0x1)
 
 /* SMCR_ELx definitions */
 #define SMCR_ELX_LEN_SHIFT		U(0)
diff --git a/include/arch/aarch64/arch_features.h b/include/arch/aarch64/arch_features.h
index d7116a7cf..a01dfe783 100644
--- a/include/arch/aarch64/arch_features.h
+++ b/include/arch/aarch64/arch_features.h
@@ -516,4 +516,30 @@ static inline bool is_feat_trbe_supported(void)
 	return read_feat_trbe_id_field() != 0U;
 
 }
+/*******************************************************************************
+ * Function to identify the presence of FEAT_SMEx (Scalar Matrix Extension)
+ ******************************************************************************/
+static inline unsigned int read_feat_sme_fa64_id_field(void)
+{
+	return ISOLATE_FIELD(read_id_aa64smfr0_el1(), ID_AA64SMFR0_EL1_SME_FA64);
+}
+
+static inline unsigned int read_feat_sme_id_field(void)
+{
+	return ISOLATE_FIELD(read_id_aa64pfr1_el1(), ID_AA64PFR1_EL1_SME);
+}
+
+static inline bool is_feat_sme_supported(void)
+{
+	if (ENABLE_SME_FOR_NS == FEAT_STATE_DISABLED) {
+		return false;
+	}
+
+	if (ENABLE_SME_FOR_NS == FEAT_STATE_ALWAYS) {
+		return true;
+	}
+
+	return read_feat_sme_id_field() >= ID_AA64PFR1_EL1_SME_SUPPORTED;
+}
+
 #endif /* ARCH_FEATURES_H */
diff --git a/include/lib/extensions/sme.h b/include/lib/extensions/sme.h
index 893f9f2cb..0e9c4b923 100644
--- a/include/lib/extensions/sme.h
+++ b/include/lib/extensions/sme.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2021-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -8,7 +8,6 @@
 #define SME_H
 
 #include <stdbool.h>
-
 #include <context.h>
 
 /*
@@ -21,7 +20,16 @@
  */
 #define SME_SMCR_LEN_MAX	U(0x1FF)
 
+#if ENABLE_SME_FOR_NS
 void sme_enable(cpu_context_t *context);
 void sme_disable(cpu_context_t *context);
+#else
+static inline void sme_enable(cpu_context_t *context)
+{
+}
+static inline void sme_disable(cpu_context_t *context)
+{
+}
+#endif /* ENABLE_SME_FOR_NS */
 
 #endif /* SME_H */
diff --git a/lib/el3_runtime/aarch64/context_mgmt.c b/lib/el3_runtime/aarch64/context_mgmt.c
index 12f3e6d03..7fbbd8171 100644
--- a/lib/el3_runtime/aarch64/context_mgmt.c
+++ b/lib/el3_runtime/aarch64/context_mgmt.c
@@ -489,10 +489,11 @@ static void manage_extensions_nonsecure(bool el2_unused, cpu_context_t *ctx)
 		amu_enable(el2_unused, ctx);
 	}
 
-#if ENABLE_SME_FOR_NS
 	/* Enable SME, SVE, and FPU/SIMD for non-secure world. */
-	sme_enable(ctx);
-#elif ENABLE_SVE_FOR_NS
+	if (is_feat_sme_supported()) {
+		sme_enable(ctx);
+	}
+#if ENABLE_SVE_FOR_NS
 	/* Enable SVE and FPU/SIMD for non-secure world. */
 	sve_enable(ctx);
 #endif
diff --git a/lib/extensions/sme/sme.c b/lib/extensions/sme/sme.c
index ec8cca82b..1846e003a 100644
--- a/lib/extensions/sme/sme.c
+++ b/lib/extensions/sme/sme.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2021-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -7,28 +7,13 @@
 #include <stdbool.h>
 
 #include <arch.h>
+#include <arch_features.h>
 #include <arch_helpers.h>
 #include <common/debug.h>
 #include <lib/el3_runtime/context_mgmt.h>
 #include <lib/extensions/sme.h>
 #include <lib/extensions/sve.h>
 
-static bool feat_sme_supported(void)
-{
-	uint64_t features;
-
-	features = read_id_aa64pfr1_el1() >> ID_AA64PFR1_EL1_SME_SHIFT;
-	return (features & ID_AA64PFR1_EL1_SME_MASK) != 0U;
-}
-
-static bool feat_sme_fa64_supported(void)
-{
-	uint64_t features;
-
-	features = read_id_aa64smfr0_el1();
-	return (features & ID_AA64SMFR0_EL1_FA64_BIT) != 0U;
-}
-
 void sme_enable(cpu_context_t *context)
 {
 	u_register_t reg;
@@ -36,7 +21,7 @@ void sme_enable(cpu_context_t *context)
 	el3_state_t *state;
 
 	/* Make sure SME is implemented in hardware before continuing. */
-	if (!feat_sme_supported()) {
+	if (!is_feat_sme_supported()) {
 		/* Perhaps the hardware supports SVE only */
 		sve_enable(context);
 		return;
@@ -66,7 +51,7 @@ void sme_enable(cpu_context_t *context)
 	 * using SMCR_EL2 and SMCR_EL1.
 	 */
 	reg = SMCR_ELX_LEN_MASK;
-	if (feat_sme_fa64_supported()) {
+	if (read_feat_sme_fa64_id_field() != 0U) {
 		VERBOSE("[SME] FA64 enabled\n");
 		reg |= SMCR_ELX_FA64_BIT;
 	}
@@ -86,7 +71,7 @@ void sme_disable(cpu_context_t *context)
 	el3_state_t *state;
 
 	/* Make sure SME is implemented in hardware before continuing. */
-	if (!feat_sme_supported()) {
+	if (!is_feat_sme_supported()) {
 		/* Perhaps the hardware supports SVE only */
 		sve_disable(context);
 		return;
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index 80c6174d1..ef917f65b 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -388,7 +388,7 @@ ENABLE_SME_FOR_NS		:= 0
 ENABLE_SME_FOR_SWD		:= 0
 
 # If SME is enabled then force SVE off
-ifeq (${ENABLE_SME_FOR_NS},1)
+ifneq (${ENABLE_SME_FOR_NS},0)
 	override ENABLE_SVE_FOR_NS	:= 0
 	override ENABLE_SVE_FOR_SWD	:= 0
 endif
diff --git a/plat/arm/board/fvp/platform.mk b/plat/arm/board/fvp/platform.mk
index 12a4a2712..caac8d48c 100644
--- a/plat/arm/board/fvp/platform.mk
+++ b/plat/arm/board/fvp/platform.mk
@@ -479,6 +479,17 @@ ENABLE_FEAT_TWED		:= 2
 ENABLE_FEAT_VHE			:= 2
 ENABLE_MPAM_FOR_LOWER_ELS	:= 2
 
+# Enable SME access to NS by default
+ifeq (${ARCH},aarch64)
+ifeq (${SPM_MM}, 0)
+ifeq (${ENABLE_RME}, 0)
+ifeq (${CTX_INCLUDE_FPREGS}, 0)
+	ENABLE_SME_FOR_NS		:= 2
+endif
+endif
+endif
+endif
+
 ifeq (${SPMC_AT_EL3}, 1)
 PLAT_BL_COMMON_SOURCES	+=	plat/arm/board/fvp/fvp_el3_spmc.c
 endif
diff --git a/services/std_svc/spm/spm_mm/spm_mm.mk b/services/std_svc/spm/spm_mm/spm_mm.mk
index f6691c372..b1f045ee6 100644
--- a/services/std_svc/spm/spm_mm/spm_mm.mk
+++ b/services/std_svc/spm/spm_mm/spm_mm.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2017-2022, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2017-2023, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -13,7 +13,7 @@ endif
 ifeq (${ENABLE_SVE_FOR_NS},1)
         $(error "Error: SPM_MM is not compatible with ENABLE_SVE_FOR_NS")
 endif
-ifeq (${ENABLE_SME_FOR_NS},1)
+ifneq (${ENABLE_SME_FOR_NS},0)
         $(error "Error: SPM_MM is not compatible with ENABLE_SME_FOR_NS")
 endif
 ifeq (${CTX_INCLUDE_FPREGS},0)
diff --git a/services/std_svc/spmd/spmd.mk b/services/std_svc/spmd/spmd.mk
index 8efbdc868..6f451c8db 100644
--- a/services/std_svc/spmd/spmd.mk
+++ b/services/std_svc/spmd/spmd.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2021, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2021-2023, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -8,7 +8,7 @@ ifneq (${ARCH},aarch64)
 	$(error "Error: SPMD is only supported on aarch64.")
 endif
 
-ifeq (${ENABLE_SME_FOR_NS},1)
+ifneq (${ENABLE_SME_FOR_NS},0)
 	$(error "Error: SPMD is not compatible with ENABLE_SME_FOR_NS")
 endif