[PATCH] RISC-V: recognize S/U mode bits in print_isa

[PATCH] RISC-V: recognize S/U mode bits in print_isa

[Patrick Stählin]

Removes the warning about an unsupported ISA when reading /proc/cpuinfo
on QEMU.

Signed-off-by: Patrick Stählin <me@packi.ch>
---
 arch/riscv/kernel/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 3a5a2ee31547..4029c7e6872b 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
 
 static void print_isa(struct seq_file *f, const char *orig_isa)
 {
-	static const char *ext = "mafdc";
+	static const char *ext = "mafdcsu";
 	const char *isa = orig_isa;
 	const char *e;
 
-- 
2.17.1

Re: [PATCH] RISC-V: recognize S/U mode bits in print_isa

[Palmer Dabbelt]

On Fri, 09 Nov 2018 11:33:47 PST (-0800), me@packi.ch wrote:
> Removes the warning about an unsupported ISA when reading /proc/cpuinfo
> on QEMU.
>
> Signed-off-by: Patrick Stählin <me@packi.ch>
> ---
>  arch/riscv/kernel/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 3a5a2ee31547..4029c7e6872b 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
>
>  static void print_isa(struct seq_file *f, const char *orig_isa)
>  {
> -	static const char *ext = "mafdc";
> +	static const char *ext = "mafdcsu";
>  	const char *isa = orig_isa;
>  	const char *e;

This is a bit pedantic, but the "S" extension should really be hidden from 
userspace.

[PATCH v2] RISC-V: recognize S/U mode bits in print_isa

[Patrick Stählin]

Removes the warning about an unsupported ISA when reading /proc/cpuinfo
on QEMU. The "S" extension is not being returned as it is not accessible
from userspace.

Signed-off-by: Patrick Stählin <me@packi.ch>
---
 arch/riscv/kernel/cpu.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 3a5a2ee31547..b4a7d4427fbb 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
 
 static void print_isa(struct seq_file *f, const char *orig_isa)
 {
-	static const char *ext = "mafdc";
+	static const char *ext = "mafdcsu";
 	const char *isa = orig_isa;
 	const char *e;
 
@@ -88,11 +88,14 @@ static void print_isa(struct seq_file *f, const char *orig_isa)
 	/*
 	 * Check the rest of the ISA string for valid extensions, printing those
 	 * we find.  RISC-V ISA strings define an order, so we only print the
-	 * extension bits when they're in order.
+	 * extension bits when they're in order. Hide the supervisor (S)
+	 * extension from userspace as it's not accessible from there.
 	 */
 	for (e = ext; *e != '\0'; ++e) {
 		if (isa[0] == e[0]) {
-			seq_write(f, isa, 1);
+			if (isa[0] != 's')
+				seq_write(f, isa, 1);
+
 			isa++;
 		}
 	}
-- 
2.17.1

Re: [PATCH v2] RISC-V: recognize S/U mode bits in print_isa

[Palmer Dabbelt]

On Fri, 09 Nov 2018 13:42:16 PST (-0800), me@packi.ch wrote:
> Removes the warning about an unsupported ISA when reading /proc/cpuinfo
> on QEMU. The "S" extension is not being returned as it is not accessible
> from userspace.
>
> Signed-off-by: Patrick Stählin <me@packi.ch>
> ---
>  arch/riscv/kernel/cpu.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 3a5a2ee31547..b4a7d4427fbb 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -64,7 +64,7 @@ int riscv_of_processor_hartid(struct device_node *node)
>
>  static void print_isa(struct seq_file *f, const char *orig_isa)
>  {
> -	static const char *ext = "mafdc";
> +	static const char *ext = "mafdcsu";
>  	const char *isa = orig_isa;
>  	const char *e;
>
> @@ -88,11 +88,14 @@ static void print_isa(struct seq_file *f, const char *orig_isa)
>  	/*
>  	 * Check the rest of the ISA string for valid extensions, printing those
>  	 * we find.  RISC-V ISA strings define an order, so we only print the
> -	 * extension bits when they're in order.
> +	 * extension bits when they're in order. Hide the supervisor (S)
> +	 * extension from userspace as it's not accessible from there.
>  	 */
>  	for (e = ext; *e != '\0'; ++e) {
>  		if (isa[0] == e[0]) {
> -			seq_write(f, isa, 1);
> +			if (isa[0] != 's')
> +				seq_write(f, isa, 1);
> +
>  			isa++;
>  		}
>  	}

This looks good to me.  I'll target it for the RCs, as it's fairly small and 
that warning fires too often.

Thanks!