riscv: hwprobe: Add support for probing V in RISCV_HWPROBE_KEY_IMA_EXT_0

Probing kernel support for Vector extension is available now. This only
add detection for V only. Extenions like Zvfh, Zk are not in this scope.
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230605110724.21391-4-andy.chiu@sifive.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/riscv/hwprobe.rst

@@ -64,6 +64,9 @@ The following keys are defined:
   * :c:macro:`RISCV_HWPROBE_IMA_C`: The C extension is supported, as defined
     by version 2.2 of the RISC-V ISA manual.
 
+  * :c:macro:`RISCV_HWPROBE_IMA_V`: The V extension is supported, as defined by
+    version 1.0 of the RISC-V Vector extension manual.
+
 * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: A bitmask that contains performance
   information about the selected set of processors.
 

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

@@ -25,6 +25,7 @@ struct riscv_hwprobe {
 #define RISCV_HWPROBE_KEY_IMA_EXT_0	4
 #define		RISCV_HWPROBE_IMA_FD		(1 << 0)
 #define		RISCV_HWPROBE_IMA_C		(1 << 1)
+#define		RISCV_HWPROBE_IMA_V		(1 << 2)
 #define RISCV_HWPROBE_KEY_CPUPERF_0	5
 #define		RISCV_HWPROBE_MISALIGNED_UNKNOWN	(0 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_EMULATED	(1 << 0)

arch/riscv/kernel/sys_riscv.c

@@ -10,6 +10,7 @@
 #include <asm/cpufeature.h>
 #include <asm/hwprobe.h>
 #include <asm/sbi.h>
+#include <asm/vector.h>
 #include <asm/switch_to.h>
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -171,6 +172,9 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 		if (riscv_isa_extension_available(NULL, c))
 			pair->value |= RISCV_HWPROBE_IMA_C;
 
+		if (has_vector())
+			pair->value |= RISCV_HWPROBE_IMA_V;
+
 		break;
 
 	case RISCV_HWPROBE_KEY_CPUPERF_0: