arm64: mops: detect and enable FEAT_MOPS

The Arm v8.8/9.3 FEAT_MOPS feature provides new instructions that
perform a memory copy or set. Wire up the cpufeature code to detect the
presence of FEAT_MOPS and enable it.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20230509142235.3284028-10-kristina.martsenko@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Author: kristina-martsenko

Documentation/arm64/cpu-feature-registers.rst

@@ -288,6 +288,8 @@ infrastructure:
      +------------------------------+---------+---------+
      | Name                         |  bits   | visible |
      +------------------------------+---------+---------+
+     | MOPS                         | [19-16] |    y    |
+     +------------------------------+---------+---------+
      | RPRES                        | [7-4]   |    y    |
      +------------------------------+---------+---------+
      | WFXT                         | [3-0]   |    y    |

Documentation/arm64/elf_hwcaps.rst

@@ -302,6 +302,9 @@ HWCAP2_SMEB16B16
 HWCAP2_SMEF16F16
     Functionality implied by ID_AA64SMFR0_EL1.F16F16 == 0b1
 
+HWCAP2_MOPS
+    Functionality implied by ID_AA64ISAR2_EL1.MOPS == 0b0001.
+
 4. Unused AT_HWCAP bits
 -----------------------
 

arch/arm64/include/asm/hwcap.h

@@ -137,6 +137,7 @@
 #define KERNEL_HWCAP_SME_BI32I32	__khwcap2_feature(SME_BI32I32)
 #define KERNEL_HWCAP_SME_B16B16		__khwcap2_feature(SME_B16B16)
 #define KERNEL_HWCAP_SME_F16F16		__khwcap2_feature(SME_F16F16)
+#define KERNEL_HWCAP_MOPS		__khwcap2_feature(MOPS)
 
 /*
  * This yields a mask that user programs can use to figure out what

arch/arm64/include/uapi/asm/hwcap.h

@@ -102,5 +102,6 @@
 #define HWCAP2_SME_BI32I32	(1UL << 40)
 #define HWCAP2_SME_B16B16	(1UL << 41)
 #define HWCAP2_SME_F16F16	(1UL << 42)
+#define HWCAP2_MOPS		(1UL << 43)
 
 #endif /* _UAPI__ASM_HWCAP_H */

arch/arm64/kernel/cpufeature.c

@@ -223,6 +223,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar2[] = {
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_CSSC_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_RPRFM_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_HIGHER_SAFE, ID_AA64ISAR2_EL1_BC_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR2_EL1_MOPS_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
 		       FTR_STRICT, FTR_EXACT, ID_AA64ISAR2_EL1_APA3_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_PTR_AUTH),
@@ -2187,6 +2188,11 @@ static void cpu_enable_dit(const struct arm64_cpu_capabilities *__unused)
 	set_pstate_dit(1);
 }
 
+static void cpu_enable_mops(const struct arm64_cpu_capabilities *__unused)
+{
+	sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_MSCEn);
+}
+
 /* Internal helper functions to match cpu capability type */
 static bool
 cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap)
@@ -2649,6 +2655,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.cpu_enable = cpu_enable_dit,
 		ARM64_CPUID_FIELDS(ID_AA64PFR0_EL1, DIT, IMP)
 	},
+	{
+		.desc = "Memory Copy and Memory Set instructions",
+		.capability = ARM64_HAS_MOPS,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		.cpu_enable = cpu_enable_mops,
+		ARM64_CPUID_FIELDS(ID_AA64ISAR2_EL1, MOPS, IMP)
+	},
 	{},
 };
 
@@ -2777,6 +2791,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(ID_AA64ISAR2_EL1, RPRFM, IMP, CAP_HWCAP, KERNEL_HWCAP_RPRFM),
 	HWCAP_CAP(ID_AA64ISAR2_EL1, RPRES, IMP, CAP_HWCAP, KERNEL_HWCAP_RPRES),
 	HWCAP_CAP(ID_AA64ISAR2_EL1, WFxT, IMP, CAP_HWCAP, KERNEL_HWCAP_WFXT),
+	HWCAP_CAP(ID_AA64ISAR2_EL1, MOPS, IMP, CAP_HWCAP, KERNEL_HWCAP_MOPS),
 #ifdef CONFIG_ARM64_SME
 	HWCAP_CAP(ID_AA64PFR1_EL1, SME, IMP, CAP_HWCAP, KERNEL_HWCAP_SME),
 	HWCAP_CAP(ID_AA64SMFR0_EL1, FA64, IMP, CAP_HWCAP, KERNEL_HWCAP_SME_FA64),

arch/arm64/kernel/cpuinfo.c

@@ -125,6 +125,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_SME_BI32I32]	= "smebi32i32",
 	[KERNEL_HWCAP_SME_B16B16]	= "smeb16b16",
 	[KERNEL_HWCAP_SME_F16F16]	= "smef16f16",
+	[KERNEL_HWCAP_MOPS]		= "mops",
 };
 
 #ifdef CONFIG_COMPAT

arch/arm64/tools/cpucaps

@@ -35,6 +35,7 @@ HAS_GIC_PRIO_RELAXED_SYNC
 HAS_HCX
 HAS_LDAPR
 HAS_LSE_ATOMICS
+HAS_MOPS
 HAS_NESTED_VIRT
 HAS_NO_FPSIMD
 HAS_NO_HW_PREFETCH