linux-kernel - Re: [PATCH v5 1/4] RISC-V: add Zbc extension detection

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Date:   Tue, 20 Jun 2023 12:09:28 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Conor Dooley <conor@...nel.org>
CC:     heiko@...ech.de, Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, herbert@...dor.apana.org.au,
        davem@...emloft.net, Conor Dooley <conor.dooley@...rochip.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, christoph.muellner@...ll.eu,
        heiko.stuebner@...ll.eu
Subject:     Re: [PATCH v5 1/4] RISC-V: add Zbc extension detection

On Mon, 12 Jun 2023 14:31:14 PDT (-0700), Conor Dooley wrote:
> Hey Heiko,
>
> On Mon, Jun 12, 2023 at 11:04:39PM +0200, Heiko Stuebner wrote:
>> From: Heiko Stuebner <heiko.stuebner@...ll.eu>
>> 
>> Add handling for Zbc extension.
>> 
>> Zbc provides instruction for carry-less multiplication.
>> 
>> Signed-off-by: Heiko Stuebner <heiko.stuebner@...ll.eu>
>> ---
>>  arch/riscv/Kconfig             | 22 ++++++++++++++++++++++
>>  arch/riscv/include/asm/hwcap.h |  1 +
>>  arch/riscv/kernel/cpu.c        |  1 +
>>  arch/riscv/kernel/cpufeature.c |  1 +
>>  4 files changed, 25 insertions(+)
>
> Plumbing into the hwprobe stuff would be nice, but that's not a
> requirement for getting stuff merged :)

IIRC we talked about this on IRC, but IMO we shouldn't require something 
be user visible for it to be merged in the kernel.

>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index a3d54cd14fca..754cd154eca5 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -523,6 +523,28 @@ config RISCV_ISA_ZBB
>>  
>>  	   If you don't know what to do here, say Y.
>>  
>> +config TOOLCHAIN_HAS_ZBC
>> +	bool
>> +	default y
>> +	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zbc)
>> +	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zbc)
>> +	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
>> +	depends on AS_IS_GNU
>> +
>> +config RISCV_ISA_ZBC
>> +	bool "Zbc extension support for bit manipulation instructions"
>> +	depends on TOOLCHAIN_HAS_ZBC
>> +	depends on !XIP_KERNEL && MMU
>> +	default y
>> +	help
>> +	   Adds support to dynamically detect the presence of the ZBC
>
> Nit: s/ZBC/Zbc/
>
> Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
>
> Cheers,
> Conor.