linux-kernel - Re: [PATCH] x86: add 'runtime constant' infrastructure

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Date: Sat, 8 Jun 2024 20:11:32 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, 
	Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] x86: add 'runtime constant' infrastructure

On Sat, 8 Jun 2024 at 13:55, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Think of this patch mostly as a "look, adding another architecture
> isn't *that* hard - even if the constant value is spread out in the
> instructions".

.. and here's a version that actually works. It wasn't that bad.

Or rather, it wouldn't have been that bad had I not spent *ages*
debugging a stupid cut-and-paste error where I instead of writing
words 0..3 of the 64-bit large constant generation, wrote words 0..2
and then overwrote word 2 (again) with the data that should have gone
into word 3. Causing the top 32 bits to be all wonky. Oops. Literally.

That stupid typo caused like two hours of wasted time.

But anyway, this patch actually works for me. It still doesn't do any
I$/D$ flushing, because it's not needed in practice, but it *should*
probably do that.

             Linus

View attachment "0001-arm64-add-runtime-const-support.patch" of type "text/x-patch" (3178 bytes)