Re: [PATCH -next v19 02/24] riscv: Extending cpufeature.c to detect V-extension

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On Tue, 09 May 2023 03:30:11 PDT (-0700), andy.chiu@xxxxxxxxxx wrote:
From: Guo Ren <ren_guo@xxxxxxxxx>

Add V-extension into riscv_isa_ext_keys array and detect it with isa
string parsing.

Signed-off-by: Guo Ren <ren_guo@xxxxxxxxx>
Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
Signed-off-by: Greentime Hu <greentime.hu@xxxxxxxxxx>
Suggested-by: Vineet Gupta <vineetg@xxxxxxxxxxxx>
Co-developed-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
Signed-off-by: Andy Chiu <andy.chiu@xxxxxxxxxx>
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Reviewed-by: Heiko Stuebner <heiko.stuebner@xxxxxxxx>
Tested-by: Heiko Stuebner <heiko.stuebner@xxxxxxxx>
---
 arch/riscv/include/asm/hwcap.h      |  1 +
 arch/riscv/include/asm/vector.h     | 26 ++++++++++++++++++++++++++
 arch/riscv/include/uapi/asm/hwcap.h |  1 +
 arch/riscv/kernel/cpufeature.c      | 11 +++++++++++
 4 files changed, 39 insertions(+)
 create mode 100644 arch/riscv/include/asm/vector.h

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index e0c40a4c63d5..574385930ba7 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -22,6 +22,7 @@
 #define RISCV_ISA_EXT_m		('m' - 'a')
 #define RISCV_ISA_EXT_s		('s' - 'a')
 #define RISCV_ISA_EXT_u		('u' - 'a')
+#define RISCV_ISA_EXT_v		('v' - 'a')

 /*
  * These macros represent the logical IDs of each multi-letter RISC-V ISA
diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
new file mode 100644
index 000000000000..427a3b51df72
--- /dev/null
+++ b/arch/riscv/include/asm/vector.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2020 SiFive
+ */
+
+#ifndef __ASM_RISCV_VECTOR_H
+#define __ASM_RISCV_VECTOR_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_RISCV_ISA_V
+
+#include <asm/hwcap.h>
+
+static __always_inline bool has_vector(void)
+{
+	return riscv_has_extension_likely(RISCV_ISA_EXT_v);

Nothing publicly availiable has V yet, so it's not likely.

+}
+
+#else /* ! CONFIG_RISCV_ISA_V  */
+
+static __always_inline bool has_vector(void) { return false; }
+
+#endif /* CONFIG_RISCV_ISA_V */
+
+#endif /* ! __ASM_RISCV_VECTOR_H */
diff --git a/arch/riscv/include/uapi/asm/hwcap.h b/arch/riscv/include/uapi/asm/hwcap.h
index 46dc3f5ee99f..c52bb7bbbabe 100644
--- a/arch/riscv/include/uapi/asm/hwcap.h
+++ b/arch/riscv/include/uapi/asm/hwcap.h
@@ -21,5 +21,6 @@
 #define COMPAT_HWCAP_ISA_F	(1 << ('F' - 'A'))
 #define COMPAT_HWCAP_ISA_D	(1 << ('D' - 'A'))
 #define COMPAT_HWCAP_ISA_C	(1 << ('C' - 'A'))
+#define COMPAT_HWCAP_ISA_V	(1 << ('V' - 'A'))

 #endif /* _UAPI_ASM_RISCV_HWCAP_H */
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index b1d6b7e4b829..7aaf92fff64e 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -107,6 +107,7 @@ void __init riscv_fill_hwcap(void)
 	isa2hwcap['f' - 'a'] = COMPAT_HWCAP_ISA_F;
 	isa2hwcap['d' - 'a'] = COMPAT_HWCAP_ISA_D;
 	isa2hwcap['c' - 'a'] = COMPAT_HWCAP_ISA_C;
+	isa2hwcap['v' - 'a'] = COMPAT_HWCAP_ISA_V;

IMO it's OK to provide V in hwcap, as there is a "V" extension defined (unlike "B", for example).


 	elf_hwcap = 0;

@@ -267,6 +268,16 @@ void __init riscv_fill_hwcap(void)
 		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
 	}

+	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
+		/*
+		 * ISA string in device tree might have 'v' flag, but
+		 * CONFIG_RISCV_ISA_V is disabled in kernel.
+		 * Clear V flag in elf_hwcap if CONFIG_RISCV_ISA_V is disabled.
+		 */
+		if (!IS_ENABLED(CONFIG_RISCV_ISA_V))
+			elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
+	}
+
 	memset(print_str, 0, sizeof(print_str));
 	for (i = 0, j = 0; i < NUM_ALPHA_EXTS; i++)
 		if (riscv_isa[0] & BIT_MASK(i))

Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>



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