linux-kernel - Re: [PATCH v5 07/16] riscv: add ISA extensions validation callback

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Date: Fri, 17 May 2024 17:44:44 +0100
From: Conor Dooley <conor@...nel.org>
To: Clément Léger <cleger@...osinc.com>
Cc: Jonathan Corbet <corbet@....net>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Anup Patel <anup@...infault.org>, Shuah Khan <shuah@...nel.org>,
	Atish Patra <atishp@...shpatra.org>, linux-doc@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v5 07/16] riscv: add ISA extensions validation callback

On Fri, May 17, 2024 at 04:52:47PM +0200, Clément Léger wrote:
> Since a few extensions (Zicbom/Zicboz) already needs validation and
> future ones will need it as well (Zc*) add a validate() callback to
> struct riscv_isa_ext_data. This require to rework the way extensions are
> parsed and split it in two phases. First phase is isa string or isa
> extension list parsing and consists in enabling all the extensions in a
> temporary bitmask (source isa) without any validation. The second step
> "resolves" the final isa bitmap, handling potential missing dependencies.
> The mechanism is quite simple and simply validate each extension
> described in the source bitmap before enabling it in the resolved isa
> bitmap. validate() callbacks can return either 0 for success,
> -EPROBEDEFER if extension needs to be validated again at next loop. A
> previous ISA bitmap is kept to avoid looping multiple times if an
> extension dependencies are never satisfied until we reach a stable
> state. In order to avoid any potential infinite looping, allow looping
> a maximum of the number of extension we handle. Zicboz and Zicbom
> extensions are modified to use this validation mechanism.

I wish we weren't doin' it at all, but since we have to, I think what
you've got here is good.
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Do you want me to send some patches for the F/V stuff we discussed
previously?

Cheers,
Conor.

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