On 22/04/2024 13:36, Conor Dooley wrote:
> On Mon, Apr 22, 2024 at 01:14:26PM +0200, Clément Léger wrote:
>> On 22/04/2024 11:35, Conor Dooley wrote:
>>> On Mon, Apr 22, 2024 at 10:53:10AM +0200, Clément Léger wrote:
>>>> On 19/04/2024 17:51, Conor Dooley wrote:
>>>>> On Thu, Apr 18, 2024 at 02:42:27PM +0200, Clément Léger wrote:
>>>>>> The Zc* standard extension for code reduction introduces new extensions.
>>>>>> This patch adds support for Zca, Zcf, Zcd and Zcb. Zce, Zcmt and Zcmp
>>>>>> are left out of this patch since they are targeting microcontrollers/
>>>>>> embedded CPUs instead of application processors.
>>>>>>
>>>>>> Signed-off-by: Clément Léger <cleger@xxxxxxxxxxxx>
>>>>>> ---
>>>>>> arch/riscv/include/asm/hwcap.h | 4 ++++
>>>>>> arch/riscv/kernel/cpufeature.c | 4 ++++
>>>>>> 2 files changed, 8 insertions(+)
>>>>>>
>>>>>> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
>>>>>> index 543e3ea2da0e..b7551bad341b 100644
>>>>>> --- a/arch/riscv/include/asm/hwcap.h
>>>>>> +++ b/arch/riscv/include/asm/hwcap.h
>>>>>> @@ -82,6 +82,10 @@
>>>>>> #define RISCV_ISA_EXT_ZACAS 73
>>>>>> #define RISCV_ISA_EXT_XANDESPMU 74
>>>>>> #define RISCV_ISA_EXT_ZIMOP 75
>>>>>> +#define RISCV_ISA_EXT_ZCA 76
>>>>>> +#define RISCV_ISA_EXT_ZCB 77
>>>>>> +#define RISCV_ISA_EXT_ZCD 78
>>>>>> +#define RISCV_ISA_EXT_ZCF 79
>>>>>>
>>>>>> #define RISCV_ISA_EXT_XLINUXENVCFG 127
>>>>>>
>>>>>> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>>>>>> index 115ba001f1bc..09dee071274d 100644
>>>>>> --- a/arch/riscv/kernel/cpufeature.c
>>>>>> +++ b/arch/riscv/kernel/cpufeature.c
>>>>>> @@ -261,6 +261,10 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>>>>>> __RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
>>>>>> __RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
>>>>>> __RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
>>>>>> + __RISCV_ISA_EXT_DATA(zca, RISCV_ISA_EXT_ZCA),
>>>>>> + __RISCV_ISA_EXT_DATA(zcb, RISCV_ISA_EXT_ZCB),
>>>>>> + __RISCV_ISA_EXT_DATA(zcd, RISCV_ISA_EXT_ZCD),
>>>>>> + __RISCV_ISA_EXT_DATA(zcf, RISCV_ISA_EXT_ZCF),
>>>>>> __RISCV_ISA_EXT_DATA(zba, RISCV_ISA_EXT_ZBA),
>>>>>> __RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZBB),
>>>>>> __RISCV_ISA_EXT_DATA(zbc, RISCV_ISA_EXT_ZBC),
>>>>>
>>>>> Ye, this looks exactly like what I "feared".
>>>>
>>>> Ok but for instance, Qemu actually set Zc* based on C/F/D. So the ISA
>>>> string containing theses dependencies should actually also be allowed.
>>>> So should we simply ignore them in the ISA string and always do our own
>>>> "post-processing" based on C/F/D?
>>>
>>> I'm not familiar with the contents of all of these extensions, but I
>>> assume the reasoning for splitting them out is that you can implement
>>> them but not maybe not implement C (or something similar)? If that's the
>>> case, you cannot always imply.
>>
>> Yeah, they can be implemented independently so we need to be able to
>> parse them independently.
>
>> However, the kernel currently requires C
>
> No it doesn't!
> There's a Kconfig option that controls whether or not we build with
> compressed instructions.
Acked, missed that. That is then advocating to keep separate Zc* extensions.
>
>> so we
>> should always have Zca/Zcf/Zcd. But if that changes in the future, then,
>> that won't be true anymore. Better keep it generic probably
>
