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[PATCH v3 3/6] RISC-V: add f & d extension validation checks

Conor Dooley posted 6 patches 1 year ago
There is a newer version of this series
[PATCH v3 3/6] RISC-V: add f & d extension validation checks
Posted by Conor Dooley 1 year ago 
From: Conor Dooley <conor.dooley@microchip.com>

Using Clement's new validation callbacks, support checking that
dependencies have been satisfied for the floating point extensions.

The check for "d" might be slightly confusingly shorter than that of "f",
despite "d" depending on "f". This is because the requirement that a
hart supporting double precision must also support single precision,
should be validated by dt-bindings etc, not the kernel but lack of
support for single precision only is a limitation of the kernel.

Since vector will now be disabled proactively, there's no need to clear
the bit in elf_hwcap in riscv_fill_hwcap() any longer.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/kernel/cpufeature.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 1c148ecea612..ad4fbaa4ff0d 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -109,6 +109,29 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
 	return 0;
 }
 
+static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
+				const unsigned long *isa_bitmap)
+{
+	if (!__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d)) {
+		pr_warn_once("This kernel does not support systems with F but not D\n");
+		return -EINVAL;
+	}
+
+	if (!IS_ENABLED(CONFIG_FPU))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int riscv_ext_d_validate(const struct riscv_isa_ext_data *data,
+				const unsigned long *isa_bitmap)
+{
+	if (!IS_ENABLED(CONFIG_FPU))
+		return -EINVAL;
+
+	return 0;
+}
+
 static int riscv_ext_vector_x_validate(const struct riscv_isa_ext_data *data,
 				       const unsigned long *isa_bitmap)
 {
@@ -368,8 +391,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(i, RISCV_ISA_EXT_i),
 	__RISCV_ISA_EXT_DATA(m, RISCV_ISA_EXT_m),
 	__RISCV_ISA_EXT_DATA(a, RISCV_ISA_EXT_a),
-	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
-	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
+	__RISCV_ISA_EXT_DATA_VALIDATE(f, RISCV_ISA_EXT_f, riscv_ext_f_validate),
+	__RISCV_ISA_EXT_DATA_VALIDATE(d, RISCV_ISA_EXT_d, riscv_ext_d_validate),
 	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
 	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(v, RISCV_ISA_EXT_v, riscv_v_exts, riscv_ext_vector_float_validate),
-- 
2.45.2
Re: [PATCH v3 3/6] RISC-V: add f & d extension validation checks
Posted by Clément Léger 1 year ago 

On 05/02/2025 17:05, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> Using Clement's new validation callbacks, support checking that
> dependencies have been satisfied for the floating point extensions.
> 
> The check for "d" might be slightly confusingly shorter than that of "f",
> despite "d" depending on "f". This is because the requirement that a
> hart supporting double precision must also support single precision,
> should be validated by dt-bindings etc, not the kernel but lack of
> support for single precision only is a limitation of the kernel.
> 
> Since vector will now be disabled proactively, there's no need to clear
> the bit in elf_hwcap in riscv_fill_hwcap() any longer.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  arch/riscv/kernel/cpufeature.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 1c148ecea612..ad4fbaa4ff0d 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -109,6 +109,29 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
>  	return 0;
>  }
>  
> +static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
> +				const unsigned long *isa_bitmap)
> +{
> +	if (!__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d)) {
> +		pr_warn_once("This kernel does not support systems with F but not D\n");
> +		return -EINVAL;
> +	}

While I tested to remove the RISCV_ISA_EXT_d from the input isa bitmap
and it worked, I didn't realized that it was due to the probe order of
single letter extensions. D is probed before F so that works as
expected. But returning -EPROBEDEFER would not allow to display the
warn_once or wrongly display it if D was not yet probed. So I'm inclined
to keep it as is and rely on probe order (a bit fragile but for single
letter extensions, that seems acceptable).

> +
> +	if (!IS_ENABLED(CONFIG_FPU))
> +		return -EINVAL;

I would have actually move that chunk before the
__riscv_isa_extension_available() check so that the whole function body
is elided if FPU is disabled.

Clément

> +
> +	return 0;
> +}

> +
> +static int riscv_ext_d_validate(const struct riscv_isa_ext_data *data,
> +				const unsigned long *isa_bitmap)
> +{
> +	if (!IS_ENABLED(CONFIG_FPU))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static int riscv_ext_vector_x_validate(const struct riscv_isa_ext_data *data,
>  				       const unsigned long *isa_bitmap)
>  {
> @@ -368,8 +391,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(i, RISCV_ISA_EXT_i),
>  	__RISCV_ISA_EXT_DATA(m, RISCV_ISA_EXT_m),
>  	__RISCV_ISA_EXT_DATA(a, RISCV_ISA_EXT_a),
> -	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
> -	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(f, RISCV_ISA_EXT_f, riscv_ext_f_validate),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(d, RISCV_ISA_EXT_d, riscv_ext_d_validate),
>  	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
>  	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(v, RISCV_ISA_EXT_v, riscv_v_exts, riscv_ext_vector_float_validate),
Re: [PATCH v3 3/6] RISC-V: add f & d extension validation checks
Posted by Conor Dooley 1 year ago 
On Tue, Feb 11, 2025 at 11:22:13AM +0100, Clément Léger wrote:
> 
> 
> On 05/02/2025 17:05, Conor Dooley wrote:
> > From: Conor Dooley <conor.dooley@microchip.com>
> > 
> > Using Clement's new validation callbacks, support checking that
> > dependencies have been satisfied for the floating point extensions.
> > 
> > The check for "d" might be slightly confusingly shorter than that of "f",
> > despite "d" depending on "f". This is because the requirement that a
> > hart supporting double precision must also support single precision,
> > should be validated by dt-bindings etc, not the kernel but lack of
> > support for single precision only is a limitation of the kernel.
> > 
> > Since vector will now be disabled proactively, there's no need to clear
> > the bit in elf_hwcap in riscv_fill_hwcap() any longer.
> > 
> > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > ---
> >  arch/riscv/kernel/cpufeature.c | 27 +++++++++++++++++++++++++--
> >  1 file changed, 25 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > index 1c148ecea612..ad4fbaa4ff0d 100644
> > --- a/arch/riscv/kernel/cpufeature.c
> > +++ b/arch/riscv/kernel/cpufeature.c
> > @@ -109,6 +109,29 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
> >  	return 0;
> >  }
> >  
> > +static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
> > +				const unsigned long *isa_bitmap)
> > +{
> > +	if (!__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d)) {
> > +		pr_warn_once("This kernel does not support systems with F but not D\n");
> > +		return -EINVAL;
> > +	}
> 
> While I tested to remove the RISCV_ISA_EXT_d from the input isa bitmap
> and it worked, I didn't realized that it was due to the probe order of
> single letter extensions. D is probed before F so that works as
> expected. But returning -EPROBEDEFER would not allow to display the
> warn_once or wrongly display it if D was not yet probed. So I'm inclined
> to keep it as is and rely on probe order (a bit fragile but for single
> letter extensions, that seems acceptable).

I guess it's worth adding a comment to that effect.

> > +
> > +	if (!IS_ENABLED(CONFIG_FPU))
> > +		return -EINVAL;
> 
> I would have actually move that chunk before the
> __riscv_isa_extension_available() check so that the whole function body
> is elided if FPU is disabled.

I think you're right, but for another reason too - warning when someone
has turned off CONIFG_FPU doesn't make sense.
Re: [PATCH v3 3/6] RISC-V: add f & d extension validation checks
Posted by Clément Léger 1 year ago 

On 05/02/2025 17:05, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> Using Clement's new validation callbacks, support checking that
> dependencies have been satisfied for the floating point extensions.
> 
> The check for "d" might be slightly confusingly shorter than that of "f",
> despite "d" depending on "f". This is because the requirement that a
> hart supporting double precision must also support single precision,
> should be validated by dt-bindings etc, not the kernel but lack of
> support for single precision only is a limitation of the kernel.
> 
> Since vector will now be disabled proactively, there's no need to clear
> the bit in elf_hwcap in riscv_fill_hwcap() any longer.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  arch/riscv/kernel/cpufeature.c | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 1c148ecea612..ad4fbaa4ff0d 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -109,6 +109,29 @@ static int riscv_ext_zicboz_validate(const struct riscv_isa_ext_data *data,
>  	return 0;
>  }
>  
> +static int riscv_ext_f_validate(const struct riscv_isa_ext_data *data,
> +				const unsigned long *isa_bitmap)
> +{
> +	if (!__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_d)) {
> +		pr_warn_once("This kernel does not support systems with F but not D\n");
> +		return -EINVAL;
> +	}
> +
> +	if (!IS_ENABLED(CONFIG_FPU))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static int riscv_ext_d_validate(const struct riscv_isa_ext_data *data,
> +				const unsigned long *isa_bitmap)
> +{
> +	if (!IS_ENABLED(CONFIG_FPU))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static int riscv_ext_vector_x_validate(const struct riscv_isa_ext_data *data,
>  				       const unsigned long *isa_bitmap)
>  {
> @@ -368,8 +391,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(i, RISCV_ISA_EXT_i),
>  	__RISCV_ISA_EXT_DATA(m, RISCV_ISA_EXT_m),
>  	__RISCV_ISA_EXT_DATA(a, RISCV_ISA_EXT_a),
> -	__RISCV_ISA_EXT_DATA(f, RISCV_ISA_EXT_f),
> -	__RISCV_ISA_EXT_DATA(d, RISCV_ISA_EXT_d),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(f, RISCV_ISA_EXT_f, riscv_ext_f_validate),
> +	__RISCV_ISA_EXT_DATA_VALIDATE(d, RISCV_ISA_EXT_d, riscv_ext_d_validate),
>  	__RISCV_ISA_EXT_DATA(q, RISCV_ISA_EXT_q),
>  	__RISCV_ISA_EXT_SUPERSET(c, RISCV_ISA_EXT_c, riscv_c_exts),
>  	__RISCV_ISA_EXT_SUPERSET_VALIDATE(v, RISCV_ISA_EXT_v, riscv_v_exts, riscv_ext_vector_float_validate),

Hi Conor,

Tested-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Clément Léger <cleger@rivosinc.com>

Thanks,

Clément

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