riscv: hwprobe: Add MIPS vendor extension probing

Add a new hwprobe key "RISCV_HWPROBE_KEY_VENDOR_EXT_MIPS_0" which allows
userspace to probe for the new xmipsexectl vendor extension.

Signed-off-by: Aleksa Paunovic <aleksa.paunovic@htecgroup.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250724-p8700-pause-v5-4-a6cbbe1c3412@htecgroup.com
[pjw@kernel.org: fixed some checkpatch issues]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

arch/riscv/include/asm/hwprobe.h

@@ -8,7 +8,7 @@
 
 #include <uapi/asm/hwprobe.h>
 
-#define RISCV_HWPROBE_MAX_KEY 13
+#define RISCV_HWPROBE_MAX_KEY 14
 
 static inline bool riscv_hwprobe_key_is_valid(__s64 key)
 {
@@ -22,6 +22,7 @@ static inline bool hwprobe_key_is_bitmask(__s64 key)
 	case RISCV_HWPROBE_KEY_IMA_EXT_0:
 	case RISCV_HWPROBE_KEY_CPUPERF_0:
 	case RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0:
+	case RISCV_HWPROBE_KEY_VENDOR_EXT_MIPS_0:
 	case RISCV_HWPROBE_KEY_VENDOR_EXT_SIFIVE_0:
 		return true;
 	}

arch/riscv/include/asm/vendor_extensions/mips_hwprobe.h

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#ifndef _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_HWPROBE_H_
+#define _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_HWPROBE_H_
+
+#include <linux/cpumask.h>
+#include <uapi/asm/hwprobe.h>
+
+#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_MIPS
+void hwprobe_isa_vendor_ext_mips_0(struct riscv_hwprobe *pair, const struct cpumask *cpus);
+#else
+static inline void hwprobe_isa_vendor_ext_mips_0(struct riscv_hwprobe *pair,
+						 const struct cpumask *cpus)
+{
+	pair->value = 0;
+}
+#endif
+
+#endif // _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_HWPROBE_H_

arch/riscv/include/uapi/asm/hwprobe.h

@@ -106,6 +106,7 @@ struct riscv_hwprobe {
 #define RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0	11
 #define RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE	12
 #define RISCV_HWPROBE_KEY_VENDOR_EXT_SIFIVE_0	13
+#define RISCV_HWPROBE_KEY_VENDOR_EXT_MIPS_0	14
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
 /* Flags */

arch/riscv/include/uapi/asm/vendor/mips.h

@@ -0,0 +1,3 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#define RISCV_HWPROBE_VENDOR_EXT_XMIPSEXECTL	BIT(0)

arch/riscv/kernel/sys_hwprobe.c

@@ -15,6 +15,7 @@
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 #include <asm/vector.h>
+#include <asm/vendor_extensions/mips_hwprobe.h>
 #include <asm/vendor_extensions/sifive_hwprobe.h>
 #include <asm/vendor_extensions/thead_hwprobe.h>
 #include <vdso/vsyscall.h>
@@ -307,6 +308,9 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 	case RISCV_HWPROBE_KEY_VENDOR_EXT_THEAD_0:
 		hwprobe_isa_vendor_ext_thead_0(pair, cpus);
 		break;
+	case RISCV_HWPROBE_KEY_VENDOR_EXT_MIPS_0:
+		hwprobe_isa_vendor_ext_mips_0(pair, cpus);
+		break;
 
 	/*
 	 * For forward compatibility, unknown keys don't fail the whole

arch/riscv/kernel/vendor_extensions/Makefile

@@ -2,6 +2,7 @@
 
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_ANDES)	+= andes.o
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_MIPS)  	+= mips.o
+obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_MIPS)  	+= mips_hwprobe.o
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_SIFIVE)	+= sifive.o
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_SIFIVE)	+= sifive_hwprobe.o
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_THEAD)	+= thead.o

arch/riscv/kernel/vendor_extensions/mips_hwprobe.c

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#include <asm/vendor_extensions.h>
+#include <asm/vendor_extensions/mips.h>
+#include <asm/vendor_extensions/mips_hwprobe.h>
+#include <asm/vendor_extensions/vendor_hwprobe.h>
+
+#include <linux/cpumask.h>
+#include <linux/types.h>
+
+#include <uapi/asm/hwprobe.h>
+#include <uapi/asm/vendor/mips.h>
+
+void hwprobe_isa_vendor_ext_mips_0(struct riscv_hwprobe *pair,
+				   const struct cpumask *cpus)
+{
+	VENDOR_EXTENSION_SUPPORTED(pair, cpus,
+				   riscv_isa_vendor_ext_list_mips.per_hart_isa_bitmap,
+				   { VENDOR_EXT_KEY(XMIPSEXECTL); });
+}