linux-kernel - Re: [RFC PATCH 09/12] riscv: Add support for kernel-mode FPU

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Date:   Mon, 11 Dec 2023 08:11:24 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Samuel Holland <samuel.holland@...ive.com>
Cc:     linux-arm-kernel@...ts.infradead.org, loongarch@...ts.linux.dev,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-riscv@...ts.infradead.org,
        Christoph Hellwig <hch@...radead.org>,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        linux-arch@...r.kernel.org
Subject: Re: [RFC PATCH 09/12] riscv: Add support for kernel-mode FPU

> +#ifdef __riscv_f
> +
> +#define kernel_fpu_begin() \
> +	static_assert(false, "floating-point code must use a separate translation unit")
> +#define kernel_fpu_end() kernel_fpu_begin()
> +
> +#else
> +
> +void kernel_fpu_begin(void);
> +void kernel_fpu_end(void);
> +
> +#endif

I'll assume this is related to trick that places code in a separate
translation unit, but I fail to understand it.  Can you add a comment
explaining it?