[v2,07/14] LoongArch: Implement ARCH_HAS_KERNEL_FPU_SUPPORT

  LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in
asm/fpu.h, so it only needs to add kernel_fpu_available() and export
the CFLAGS adjustments.

Acked-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
---

(no changes since v1)

 arch/loongarch/Kconfig           | 1 +
 arch/loongarch/Makefile          | 5 ++++-
 arch/loongarch/include/asm/fpu.h | 1 +
 3 files changed, 6 insertions(+), 1 deletion(-)
  

Hi, Samuel,

On Thu, Dec 28, 2023 at 9:42 AM Samuel Holland
<samuel.holland@sifive.com> wrote:
>
> LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in
> asm/fpu.h, so it only needs to add kernel_fpu_available() and export
> the CFLAGS adjustments.
>
> Acked-by: WANG Xuerui <git@xen0n.name>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
>
> (no changes since v1)
>
>  arch/loongarch/Kconfig           | 1 +
>  arch/loongarch/Makefile          | 5 ++++-
>  arch/loongarch/include/asm/fpu.h | 1 +
>  3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index ee123820a476..65d4475565b8 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -15,6 +15,7 @@ config LOONGARCH
>         select ARCH_HAS_CPU_FINALIZE_INIT
>         select ARCH_HAS_FORTIFY_SOURCE
>         select ARCH_HAS_KCOV
> +       select ARCH_HAS_KERNEL_FPU_SUPPORT if CPU_HAS_FPU
>         select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
>         select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>         select ARCH_HAS_PTE_SPECIAL
> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> index 4ba8d67ddb09..1afe28feaba5 100644
> --- a/arch/loongarch/Makefile
> +++ b/arch/loongarch/Makefile
> @@ -25,6 +25,9 @@ endif
>  32bit-emul             = elf32loongarch
>  64bit-emul             = elf64loongarch
>
> +CC_FLAGS_FPU           := -mfpu=64
> +CC_FLAGS_NO_FPU                := -msoft-float
We will add LoongArch32 support later, maybe it should be -mfpu=32 in
that case, and do other archs have the case that only support FP32?

Huacai

> +
>  ifdef CONFIG_DYNAMIC_FTRACE
>  KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
>  CC_FLAGS_FTRACE := -fpatchable-function-entry=2
> @@ -46,7 +49,7 @@ ld-emul                       = $(64bit-emul)
>  cflags-y               += -mabi=lp64s
>  endif
>
> -cflags-y                       += -pipe -msoft-float
> +cflags-y                       += -pipe $(CC_FLAGS_NO_FPU)
>  LDFLAGS_vmlinux                        += -static -n -nostdlib
>
>  # When the assembler supports explicit relocation hint, we must use it.
> diff --git a/arch/loongarch/include/asm/fpu.h b/arch/loongarch/include/asm/fpu.h
> index c2d8962fda00..3177674228f8 100644
> --- a/arch/loongarch/include/asm/fpu.h
> +++ b/arch/loongarch/include/asm/fpu.h
> @@ -21,6 +21,7 @@
>
>  struct sigcontext;
>
> +#define kernel_fpu_available() cpu_has_fpu
>  extern void kernel_fpu_begin(void);
>  extern void kernel_fpu_end(void);
>
> --
> 2.42.0
>
>
  

Hi Huacai,

On 2024-01-04 3:55 AM, Huacai Chen wrote:
> Hi, Samuel,
> 
> On Thu, Dec 28, 2023 at 9:42 AM Samuel Holland
> <samuel.holland@sifive.com> wrote:
>>
>> LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in
>> asm/fpu.h, so it only needs to add kernel_fpu_available() and export
>> the CFLAGS adjustments.
>>
>> Acked-by: WANG Xuerui <git@xen0n.name>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
>> ---
>>
>> (no changes since v1)
>>
>>  arch/loongarch/Kconfig           | 1 +
>>  arch/loongarch/Makefile          | 5 ++++-
>>  arch/loongarch/include/asm/fpu.h | 1 +
>>  3 files changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index ee123820a476..65d4475565b8 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -15,6 +15,7 @@ config LOONGARCH
>>         select ARCH_HAS_CPU_FINALIZE_INIT
>>         select ARCH_HAS_FORTIFY_SOURCE
>>         select ARCH_HAS_KCOV
>> +       select ARCH_HAS_KERNEL_FPU_SUPPORT if CPU_HAS_FPU
>>         select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
>>         select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>         select ARCH_HAS_PTE_SPECIAL
>> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
>> index 4ba8d67ddb09..1afe28feaba5 100644
>> --- a/arch/loongarch/Makefile
>> +++ b/arch/loongarch/Makefile
>> @@ -25,6 +25,9 @@ endif
>>  32bit-emul             = elf32loongarch
>>  64bit-emul             = elf64loongarch
>>
>> +CC_FLAGS_FPU           := -mfpu=64
>> +CC_FLAGS_NO_FPU                := -msoft-float
> We will add LoongArch32 support later, maybe it should be -mfpu=32 in
> that case, and do other archs have the case that only support FP32?

Do you mean that LoongArch32 does not support double-precision FP in hardware?
At least both of the consumers in this series use double-precision, so my first
thought is that LoongArch32 could not select ARCH_HAS_KERNEL_FPU_SUPPORT.

Regards,
Samuel
  

On Thu, Jan 4, 2024 at 11:58 PM Samuel Holland
<samuel.holland@sifive.com> wrote:
>
> Hi Huacai,
>
> On 2024-01-04 3:55 AM, Huacai Chen wrote:
> > Hi, Samuel,
> >
> > On Thu, Dec 28, 2023 at 9:42 AM Samuel Holland
> > <samuel.holland@sifive.com> wrote:
> >>
> >> LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in
> >> asm/fpu.h, so it only needs to add kernel_fpu_available() and export
> >> the CFLAGS adjustments.
> >>
> >> Acked-by: WANG Xuerui <git@xen0n.name>
> >> Reviewed-by: Christoph Hellwig <hch@lst.de>
> >> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> >> ---
> >>
> >> (no changes since v1)
> >>
> >>  arch/loongarch/Kconfig           | 1 +
> >>  arch/loongarch/Makefile          | 5 ++++-
> >>  arch/loongarch/include/asm/fpu.h | 1 +
> >>  3 files changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> >> index ee123820a476..65d4475565b8 100644
> >> --- a/arch/loongarch/Kconfig
> >> +++ b/arch/loongarch/Kconfig
> >> @@ -15,6 +15,7 @@ config LOONGARCH
> >>         select ARCH_HAS_CPU_FINALIZE_INIT
> >>         select ARCH_HAS_FORTIFY_SOURCE
> >>         select ARCH_HAS_KCOV
> >> +       select ARCH_HAS_KERNEL_FPU_SUPPORT if CPU_HAS_FPU
> >>         select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
> >>         select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> >>         select ARCH_HAS_PTE_SPECIAL
> >> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> >> index 4ba8d67ddb09..1afe28feaba5 100644
> >> --- a/arch/loongarch/Makefile
> >> +++ b/arch/loongarch/Makefile
> >> @@ -25,6 +25,9 @@ endif
> >>  32bit-emul             = elf32loongarch
> >>  64bit-emul             = elf64loongarch
> >>
> >> +CC_FLAGS_FPU           := -mfpu=64
> >> +CC_FLAGS_NO_FPU                := -msoft-float
> > We will add LoongArch32 support later, maybe it should be -mfpu=32 in
> > that case, and do other archs have the case that only support FP32?
>
> Do you mean that LoongArch32 does not support double-precision FP in hardware?
> At least both of the consumers in this series use double-precision, so my first
> thought is that LoongArch32 could not select ARCH_HAS_KERNEL_FPU_SUPPORT.
Then is it possible to introduce CC_FLAGS_SP_FPU and CC_FLAGS_DP_FPU?
I think there may be some place where SP FP is enough.

Huacai

>
> Regards,
> Samuel
>
  

On Sun, Jan 07, 2024 at 10:39:07AM +0800, Huacai Chen wrote:
> > Do you mean that LoongArch32 does not support double-precision FP in hardware?
> > At least both of the consumers in this series use double-precision, so my first
> > thought is that LoongArch32 could not select ARCH_HAS_KERNEL_FPU_SUPPORT.
> Then is it possible to introduce CC_FLAGS_SP_FPU and CC_FLAGS_DP_FPU?
> I think there may be some place where SP FP is enough.

Let's defer that until it is actually neeed.