linux-kernel - Re: [PATCH v8 4/7] x86/mm: Simplify clear_page

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Message-ID: <20251028133648.GAaQDG8PfOwrSiHYuk@fat_crate.local>
Date: Tue, 28 Oct 2025 14:36:48 +0100
From: Borislav Petkov <bp@...en8.de>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
	akpm@...ux-foundation.org, david@...hat.com,
	dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
	mjguzik@...il.com, luto@...nel.org, peterz@...radead.org,
	acme@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
	willy@...radead.org, raghavendra.kt@....com,
	boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v8 4/7] x86/mm: Simplify clear_page_*

On Mon, Oct 27, 2025 at 01:21:06PM -0700, Ankur Arora wrote:
> +/**
> + * clear_page() - clear a page using a kernel virtual address.
> + * @addr: address of kernel page
> + *
> + * Switch between three implementations of page clearing based on CPU
> + * capabilities:
> + *
> + *  - memzero_page_aligned_unrolled(): the oldest, slowest and universally

So I don't see how a memzero_<bla> name shows that it belongs to the
clear_page "stack" of functions? clear_page_orig() kinda conveys better what
this thing is. In any case, having "clear_page" somewhere there in the name
should stay.

> + *    supported method. Zeroes via 8-byte MOV instructions unrolled 8x
> + *    to write a 64-byte cacheline in each loop iteration..
							    ^

one fullstop is enough.

> + *
> + *  - "rep stosq": really old CPUs had crummy REP implementations.

We spell all x86 insns in ALL CAPS. Like you've almost done.

Also, it is

	REP; STOSQ

with a ;

Otherwise the idea for the cleanup makes sense.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette