linux-kernel - Re: [PATCH v2 05/19] riscv: add ISA extension parsing for vector crypto extensions

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Message-Id: <E30E7352-1FB0-4DB5-94C3-2C6FC2A6F484@sifive.com>
Date:   Fri, 20 Oct 2023 10:43:26 +0800
From:   Jerry Shih <jerry.shih@...ive.com>
To:     Clément Léger <cleger@...osinc.com>
Cc:     Evan Green <evan@...osinc.com>, linux-riscv@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Palmer Dabbelt <palmer@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Jonathan Corbet <corbet@....net>,
        Andrew Jones <ajones@...tanamicro.com>,
        Conor Dooley <conor@...nel.org>,
        Samuel Ortiz <sameo@...osinc.com>
Subject: Re: [PATCH v2 05/19] riscv: add ISA extension parsing for vector
 crypto extensions

On Oct 19, 2023, at 17:35, Clément Léger <cleger@...osinc.com> wrote:
> On 18/10/2023 19:26, Evan Green wrote:
>> On Wed, Oct 18, 2023 at 5:53 AM Clément Léger <cleger@...osinc.com> wrote:
>>> 
>>> On 18/10/2023 03:45, Jerry Shih wrote:
>>>> 
>>>> The `Zvkb` is the subset of `Zvbb`[1]. So, the `Zvkb` should be bundled with `Zvbb`.
>>> 
>>> Hi Jerry,
>>> 
>>> Thanks for catching this, I think some other extensions will fall in
>>> this category as well then (Zvknha/Zvknhb). I will verify that.
>> 
>> The bundling mechanism works well when an extension is a pure lasso
>> around other extensions. We'd have to tweak that code if we wanted to
>> support cases like this, where the extension is a superset of others,
>> but also contains loose change not present anywhere else (and
>> therefore also needs to stand as a separate bit).
> 
> For Zvbb and Zvknhb, I used the following code:
> 
> static const unsigned int riscv_zvbb_bundled_exts[] = {
> 	RISCV_ISA_EXT_ZVKB,
> 	RISCV_ISA_EXT_ZVBB
> };
> 
> static const unsigned int riscv_zvknhb_bundled_exts[] = {
> 	RISCV_ISA_EXT_ZVKNHA,
> 	RISCV_ISA_EXT_ZVKNHB
> };
> 
> Which correctly results in both extension (superset + base set) being
> enabled when only one is set. Is there something that I'm missing ?

We should not bundle zvknha and zvknhb together. They are exclusive.
Please check:
https://github.com/riscv/riscv-crypto/issues/364#issuecomment-1726782096

-Jerry