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Date:   Thu, 16 Jun 2022 15:04:50 -0700 (PDT)
Subject:     Re: [PATCH v2 0/2] introduce unified static key mechanism for ISA ext
In-Reply-To: <20220522153543.2656-1-jszhang@kernel.org>
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        atishp@atishpatra.org, anup@brainfault.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     jszhang@kernel.org
Message-ID: <mhng-ea1ebe26-82ad-4a9d-b024-f6d79a0cb699@palmer-ri-x1c9>
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On Sun, 22 May 2022 08:35:41 PDT (-0700), jszhang@kernel.org wrote:
> Currently, riscv has several extensions which may not be supported on all
> riscv platforms, for example, FPU and so on. To support unified kernel
> Image style, we need to check whether the feature is supported or not.
> If the check sits at hot code path, the performance will be impacted a
> lot. static key can be used to solve the issue. In the past, FPU
> support has been converted to use static key mechanism. I believe we
> will have similar cases in the future.
>
> Since v1:
>   - fix typo, thank Atish
>   - remove riscv_isa_have_key_extension() instead use the isa ext keys
>     directly as pointed out by Atish.
>
> Jisheng Zhang (2):
>   riscv: introduce unified static key mechanism for ISA extensions
>   riscv: switch has_fpu() to the unified static key mechanism
>
>  arch/riscv/include/asm/hwcap.h     | 25 +++++++++++++++++++++++++
>  arch/riscv/include/asm/switch_to.h |  4 ++--
>  arch/riscv/kernel/cpufeature.c     | 14 +++++++-------
>  3 files changed, 34 insertions(+), 9 deletions(-)

Thanks, this is on for-next.