linux-kernel - Re: [PATCH] mm: use clear_user_(high)page() for arch with special user folio handling

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Message-ID: <Z1Mpfofz45bFawSq@casper.infradead.org>
Date: Fri, 6 Dec 2024 16:42:38 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Zi Yan <ziy@...dia.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	David Hildenbrand <david@...hat.com>,
	Miaohe Lin <linmiaohe@...wei.com>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	John Hubbard <jhubbard@...dia.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Alexander Potapenko <glider@...gle.com>,
	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Vineet Gupta <vgupta@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] mm: use clear_user_(high)page() for arch with special
 user folio handling

On Fri, Dec 06, 2024 at 09:19:38AM -0500, Zi Yan wrote:
> For architectures setting ARCH_HAS_CPU_CACHE_ALIASING, which requires
> flushing cache and arc, which sets folio->flags after clearing a user
> folio

I think arc just has some legacy code left that needs to be ripped out.
See commit d5272aaa8257 which took away ARCH_HAS_CPU_CACHE_ALIASING
from arc.

Looking at 8690bbcf3b70, I wonder if you want to use
cpu_dcache_is_aliasing() here?