Re: [PATCH -next v13 02/19] riscv: Extending cpufeature.c to detect V-extension

Conor Dooley
2023-01-28T10:28:41Z

On 28 January 2023 07:09:18 GMT, Guo Ren <guoren@kernel.org> wrote:
>On Thu, Jan 26, 2023 at 5:33 AM Conor Dooley <conor@kernel.org> wrote:
>>
>> On Wed, Jan 25, 2023 at 02:20:39PM +0000, Andy Chiu wrote:
>> > From: Guo Ren <ren_guo@c-sky.com>
>> >
>> > Add V-extension into riscv_isa_ext_keys array and detect it with isa
>> > string parsing.
>> >
>> > Signed-off-by: Guo Ren <ren_guo@c-sky.com>
>> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
>> > Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
>> > Suggested-by: Vineet Gupta <vineetg@rivosinc.com>
>> > Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
>> > ---
>> > arch/riscv/include/asm/hwcap.h | 4 ++++
>> > arch/riscv/include/asm/vector.h | 26 ++++++++++++++++++++++++++
>> > arch/riscv/include/uapi/asm/hwcap.h | 1 +
>> > arch/riscv/kernel/cpufeature.c | 12 ++++++++++++
>> > 4 files changed, 43 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 57439da71c77..f413db6118e5 100644
>> > --- a/arch/riscv/include/asm/hwcap.h
>> > +++ b/arch/riscv/include/asm/hwcap.h
>> > @@ -35,6 +35,7 @@ extern unsigned long elf_hwcap;
>> > #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')
>> >
>> > /*
>> > * Increse this to higher value as kernel support more ISA extensions.
>> > @@ -73,6 +74,7 @@ static_assert(RISCV_ISA_EXT_ID_MAX <= RISCV_ISA_EXT_MAX);
>> > enum riscv_isa_ext_key {
>> > RISCV_ISA_EXT_KEY_FPU, /* For 'F' and 'D' */
>> > RISCV_ISA_EXT_KEY_SVINVAL,
>> > + RISCV_ISA_EXT_KEY_VECTOR, /* For 'V' */
>>
>> That's obvious surely, no?
>>
>> > RISCV_ISA_EXT_KEY_ZIHINTPAUSE,
>> > RISCV_ISA_EXT_KEY_MAX,
>> > };
>> > @@ -95,6 +97,8 @@ static __always_inline int riscv_isa_ext2key(int num)
>>
>> You should probably check out Jisheng's series that deletes whole
>> sections of this code, including this whole function.
>> https://lore.kernel.org/all/20230115154953.831-3-jszhang@kernel.org/T/#u
>Has that patch merged? It could be solved during the rebase for-next naturally.

Not merged yet. Pretty sure Andy used for-next
as his base so that CI could test it more easily
I was just pointing out it's existence in case he
hadn't seen it.
Hopefully Jishengs stuff will make 6.3 :)

>
>>
>>
>> > @@ -256,6 +257,17 @@ void __init riscv_fill_hwcap(void)
>> > elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
>> > }
>> >
>> > + if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
>> > +#ifndef CONFIG_RISCV_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.
>> > + */
>> > + elf_hwcap &= ~COMPAT_HWCAP_ISA_V;
>> > +#endif
> if (elf_hwcap & COMPAT_HWCAP_ISA_V && !IS_ENABLED(CONFIG_RISCV_ISA_V)) {
>
>right?
>>
>> I know that a later patch in this series calls rvv_enable() here, which
>> I'll comment on there, but I'd rather see IS_ENABLED as opposed to
>> ifdefs in C files where possible.
>>
>> Thanks,
>> Conor.
>>
>
>