linux-kernel - Re: [PATCH] riscv: Make sure toolchain supports zba before using zba instructions

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Message-ID: <c0f425ec-6c76-45b2-b1bc-8d9be028a878@rivosinc.com>
Date: Fri, 28 Mar 2025 14:02:08 +0100
From: Clément Léger <cleger@...osinc.com>
To: Alexandre Ghiti <alex@...ti.fr>, Alexandre Ghiti <alexghiti@...osinc.com>
Cc: kernel test robot <lkp@...el.com>,
 Paul Walmsley <paul.walmsley@...ive.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...belt.com>
Subject: Re: [PATCH] riscv: Make sure toolchain supports zba before using zba
 instructions



On 28/03/2025 14:00, Alexandre Ghiti wrote:
> On 28/03/2025 13:51, Clément Léger wrote:
>>
>> On 28/03/2025 12:54, Alexandre Ghiti wrote:
>>> Old toolchain like gcc 8.5.0 does not support zba, so we must check that
>>> the toolchain supports this extension before using it in the kernel.
>>>
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Closes: https://lore.kernel.org/oe-kbuild-all/202503281836.8pntHm6I-
>>> lkp@...el.com/
>>> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
>>> ---
>>>   arch/riscv/Kconfig                     | 8 ++++++++
>>>   arch/riscv/include/asm/runtime-const.h | 5 +++--
>>>   2 files changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>>> index 0d8def968a7e..ae6303f15b28 100644
>>> --- a/arch/riscv/Kconfig
>>> +++ b/arch/riscv/Kconfig
>>> @@ -735,6 +735,14 @@ config TOOLCHAIN_HAS_VECTOR_CRYPTO
>>>       def_bool $(as-instr, .option arch$(comma) +v$(comma) +zvkb)
>>>       depends on AS_HAS_OPTION_ARCH
>>>   +config TOOLCHAIN_HAS_ZBA
>>> +    bool
>>> +    default y
>>> +    depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zba)
>>> +    depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zba)
>>> +    depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
>>> +    depends on AS_HAS_OPTION_ARCH
>>> +
>>>   config RISCV_ISA_ZBA
>> Hi Alex,
>>
>> Why not add a "depends on TOOLCHAIN_HAS_ZBA" here so you don't have to
>> check for that config option when using CONFIG_RISCV_ISA_ZBA ? This is
>> done like that for ZBB and ZBC.
> 
> 
> Actually Conor changed that for Zbb in https://lore.kernel.org/
> lkml/20241024-aspire-rectify-9982da6943e5@...d/T/
> #m89d45ba3cbc6c2f953516c0e9977fecf397809b0 which is queued for 6.15.
> 
> Zba is also used in BPF, so we should not require that the toolchain
> supports zba but instead just that the platform supports it.

Indeed, makes sense !

Thanks,

Clément

> 
> Thanks,
> 
> Alex
> 
> 
>>
>> Thanks,
>>
>> Clément
>>
>>>       bool "Zba extension support for bit manipulation instructions"
>>>       default y
>>> diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/
>>> include/asm/runtime-const.h
>>> index ea2e49c7149c..c07d049fdd5d 100644
>>> --- a/arch/riscv/include/asm/runtime-const.h
>>> +++ b/arch/riscv/include/asm/runtime-const.h
>>> @@ -77,7 +77,8 @@
>>>       ".long 1b - .\n\t"                    \
>>>       ".popsection"                        \
>>>   -#if defined(CONFIG_RISCV_ISA_ZBA) && defined(CONFIG_RISCV_ISA_ZBKB)
>>> +#if defined(CONFIG_RISCV_ISA_ZBA) &&
>>> defined(CONFIG_TOOLCHAIN_HAS_ZBA)    \
>>> +    && defined(CONFIG_RISCV_ISA_ZBKB)
>>
>>>   #define runtime_const_ptr(sym)                        \
>>>   ({                                    \
>>>       typeof(sym) __ret, __tmp;                    \
>>> @@ -93,7 +94,7 @@
>>>           : [__ret] "=r" (__ret), [__tmp] "=r" (__tmp));        \
>>>       __ret;                                \
>>>   })
>>> -#elif defined(CONFIG_RISCV_ISA_ZBA)
>>> +#elif defined(CONFIG_RISCV_ISA_ZBA) &&
>>> defined(CONFIG_TOOLCHAIN_HAS_ZBA)
>>>   #define runtime_const_ptr(sym)                        \
>>>   ({                                    \
>>>       typeof(sym) __ret, __tmp;                    \