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Date: Thu, 3 Sep 2026 07:49:49 +0200
From: Christoph Hellwig <hch@lst.de>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
	x86@kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH RESEND] xor: add missing vzeroupper to AVX code
Message-ID: <20260903054949.GA16883@lst.de>
References: <20260831212248.213805-1-ebiggers@kernel.org> <20260902133706.GA21538@lst.de> <20260902162359.GA2497@quark>
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On Wed, Sep 02, 2026 at 09:23:59AM -0700, Eric Biggers wrote:
> > 
> > Can we do kernel_avx_{begin,end} instead of having to open code
> > and document this everywhere, please?
> 
> Again, there are cases in the kernel where both AVX and SSE are used
> within a single kernel-mode FPU section, or where a CPU feature check
> occurs within the section and one or the other is used.  So that
> abstraction will not work as-is,

So don't use it for that one case (which I've seen, but make it two or
three and the same still applies), and everyone else gets to use the
easy case.

> and it would be different from all
> userspace code as well.

I don't know how you defined "all".  Almost no userspace code has
kernel_fpu_{begin,end} to start with.  The one code base I've recently
ported to the kernel that has it, also has kernel_avx_{begin,end}
already.