Two updates for RISC-V -march warnings

Two updates for RISC-V -march warnings

[Ben Dooks]

Updates to remove warnings from latest kernel builds.

[PATCH 1/2] RISC-V: Stop warning about Zabha and Zacas

[Ben Dooks]

The zabha (atomic byte and halfword) and zacas (atomic compare/swap)
are now being used by the kernel, so parse these and stop the warnings
when running make C=1 on current kernels.

WARNING: invalid argument to '-march': '_zacas_zabha'

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 target-riscv.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target-riscv.c b/target-riscv.c
index d30be04b..80c25285 100644
--- a/target-riscv.c
+++ b/target-riscv.c
@@ -22,6 +22,8 @@
 #define RISCV_ZICBOM	(1 << 12)
 #define RISCV_ZIHINTPAUSE	(1 << 13)
 #define RISCV_VECTOR	(1 << 14)
+#define RISCV_ATOMIC_CAS (1 << 15)
+#define RISCV_ATOMIC_BH	 (1 << 16)
 
 static unsigned int riscv_flags;
 
@@ -43,6 +45,8 @@ static void parse_march_riscv(const char *arg)
 		{ "d",		RISCV_DOUBLE|RISCV_FDIV|RISCV_ZICSR },
 		{ "c",		RISCV_COMP },
 		{ "v",		RISCV_VECTOR|RISCV_FPU|RISCV_ZICSR },
+		{ "_zacas",	RISCV_ATOMIC_CAS },
+		{ "_zabha",	RISCV_ATOMIC_BH },
 		{ "_zicsr",	RISCV_ZICSR },
 		{ "_zifencei",	RISCV_ZIFENCEI },
 		{ "_zicbom",	RISCV_ZICBOM },
-- 
2.37.2.352.g3c44437643

[PATCH 2/2] RISC-V: restart extension search on match

[Ben Dooks]

If we are passed multiple extensions in -march, don't assume these will
be in any sort of order. If we do match, then restart the loop by setting
the search back to 0, and retrying.

This sorts out issues with the current kernel build where there are now
lots of extensions for the rv64i and even adding zacas doesn't silence the
warnings generated.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
 target-riscv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/target-riscv.c b/target-riscv.c
index 80c25285..ddf50e61 100644
--- a/target-riscv.c
+++ b/target-riscv.c
@@ -56,7 +56,7 @@ static void parse_march_riscv(const char *arg)
 
 	// Each -march=.. options entirely overrides previous ones
 	riscv_flags = 0;
-
+	
 	for (i = 0; i < ARRAY_SIZE(basic_sets); i++) {
 		const char *pat = basic_sets[i].pattern;
 		size_t len = strlen(pat);
@@ -80,6 +80,7 @@ ext:
 		if (!strncmp(arg, pat, len)) {
 			riscv_flags |= extensions[i].flags;
 			arg += len;
+			i = 0;
 		}
 	}
 	if (arg[0])
-- 
2.37.2.352.g3c44437643

Re: [PATCH 1/2] RISC-V: Stop warning about Zabha and Zacas

[Paul Walmsley]

On Fri, 2 Jan 2026, Ben Dooks wrote:

> The zabha (atomic byte and halfword) and zacas (atomic compare/swap)
> are now being used by the kernel, so parse these and stop the warnings
> when running make C=1 on current kernels.
> 
> WARNING: invalid argument to '-march': '_zacas_zabha'
> 
> Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>

Thanks Ben.  This saved me some time!

Tested-by: Paul Walmsley <pjw@kernel.org>


- Paul

Re: [PATCH 2/2] RISC-V: restart extension search on match

[Paul Walmsley]

On Fri, 2 Jan 2026, Ben Dooks wrote:

> If we are passed multiple extensions in -march, don't assume these will
> be in any sort of order. If we do match, then restart the loop by setting
> the search back to 0, and retrying.
> 
> This sorts out issues with the current kernel build where there are now
> lots of extensions for the rv64i and even adding zacas doesn't silence the
> warnings generated.
> 
> Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
> ---
>  target-riscv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/target-riscv.c b/target-riscv.c
> index 80c25285..ddf50e61 100644
> --- a/target-riscv.c
> +++ b/target-riscv.c
> @@ -56,7 +56,7 @@ static void parse_march_riscv(const char *arg)
>  
>  	// Each -march=.. options entirely overrides previous ones
>  	riscv_flags = 0;
> -
> +	

Looks like some horizontal whitespace was inadvertently added here.

>  	for (i = 0; i < ARRAY_SIZE(basic_sets); i++) {
>  		const char *pat = basic_sets[i].pattern;
>  		size_t len = strlen(pat);
> @@ -80,6 +80,7 @@ ext:
>  		if (!strncmp(arg, pat, len)) {
>  			riscv_flags |= extensions[i].flags;
>  			arg += len;
> +			i = 0;
>  		}
>  	}
>  	if (arg[0])


Tested-by: Paul Walmsley <pjw@kernel.org>


- Paul