riscv: Add xmipsexectl as a vendor extension

Add support for MIPS vendor extensions. Add support for the 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-v5-2-a6cbbe1c3412@htecgroup.com
[pjw@kernel.org: added the MIPS vendor ID from another patch to fix the build]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

arch/riscv/Kconfig.vendor

@@ -16,6 +16,19 @@ config RISCV_ISA_VENDOR_EXT_ANDES
 	  If you don't know what to do here, say Y.
 endmenu
 
+menu "MIPS"
+config RISCV_ISA_VENDOR_EXT_MIPS
+	bool "MIPS vendor extension support"
+	select RISCV_ISA_VENDOR_EXT
+	default y
+	help
+	  Say N here to disable detection of and support for all MIPS vendor
+	  extensions. Without this option enabled, MIPS vendor extensions will
+	  not be detected at boot and their presence not reported to userspace.
+
+	  If you don't know what to do here, say Y.
+endmenu
+
 menu "SiFive"
 config RISCV_ISA_VENDOR_EXT_SIFIVE
 	bool "SiFive vendor extension support"

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

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#ifndef _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_H
+#define _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_H
+
+#include <linux/types.h>
+
+#define RISCV_ISA_VENDOR_EXT_XMIPSEXECTL	0
+
+#ifndef __ASSEMBLER__
+struct riscv_isa_vendor_ext_data_list;
+extern struct riscv_isa_vendor_ext_data_list riscv_isa_vendor_ext_list_mips;
+#endif
+
+#endif // _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_H

arch/riscv/include/asm/vendorid_list.h

@@ -9,5 +9,6 @@
 #define MICROCHIP_VENDOR_ID	0x029
 #define SIFIVE_VENDOR_ID	0x489
 #define THEAD_VENDOR_ID		0x5b7
+#define MIPS_VENDOR_ID		0x722
 
 #endif

arch/riscv/kernel/vendor_extensions.c

@@ -6,6 +6,7 @@
 #include <asm/vendorid_list.h>
 #include <asm/vendor_extensions.h>
 #include <asm/vendor_extensions/andes.h>
+#include <asm/vendor_extensions/mips.h>
 #include <asm/vendor_extensions/sifive.h>
 #include <asm/vendor_extensions/thead.h>
 
@@ -16,6 +17,9 @@ struct riscv_isa_vendor_ext_data_list *riscv_isa_vendor_ext_list[] = {
 #ifdef CONFIG_RISCV_ISA_VENDOR_EXT_ANDES
 	&riscv_isa_vendor_ext_list_andes,
 #endif
+#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_MIPS
+	&riscv_isa_vendor_ext_list_mips,
+#endif
 #ifdef CONFIG_RISCV_ISA_VENDOR_EXT_SIFIVE
 	&riscv_isa_vendor_ext_list_sifive,
 #endif
@@ -49,6 +53,12 @@ bool __riscv_isa_vendor_extension_available(int cpu, unsigned long vendor, unsig
 		cpu_bmap = riscv_isa_vendor_ext_list_andes.per_hart_isa_bitmap;
 		break;
 	#endif
+	#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_MIPS
+	case MIPS_VENDOR_ID:
+		bmap = &riscv_isa_vendor_ext_list_mips.all_harts_isa_bitmap;
+		cpu_bmap = riscv_isa_vendor_ext_list_mips.per_hart_isa_bitmap;
+		break;
+	#endif
 	#ifdef CONFIG_RISCV_ISA_VENDOR_EXT_SIFIVE
 	case SIFIVE_VENDOR_ID:
 		bmap = &riscv_isa_vendor_ext_list_sifive.all_harts_isa_bitmap;

arch/riscv/kernel/vendor_extensions/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_ANDES)	+= andes.o
+obj-$(CONFIG_RISCV_ISA_VENDOR_EXT_MIPS)  	+= mips.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.c

@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#include <asm/cpufeature.h>
+#include <asm/vendor_extensions.h>
+#include <asm/vendor_extensions/mips.h>
+
+#include <linux/array_size.h>
+#include <linux/cpumask.h>
+#include <linux/types.h>
+
+/* All MIPS vendor extensions supported in Linux */
+static const struct riscv_isa_ext_data riscv_isa_vendor_ext_mips[] = {
+	__RISCV_ISA_EXT_DATA(xmipsexectl, RISCV_ISA_VENDOR_EXT_XMIPSEXECTL),
+};
+
+struct riscv_isa_vendor_ext_data_list riscv_isa_vendor_ext_list_mips = {
+	.ext_data_count = ARRAY_SIZE(riscv_isa_vendor_ext_mips),
+	.ext_data = riscv_isa_vendor_ext_mips,
+};