linux-kernel - Re: [PATCH] arm64: mm: use ptep_clear() instead of pte_clear() in clear

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Message-ID: <20230811110311.GB6993@willie-the-truck>
Date:   Fri, 11 Aug 2023 12:03:12 +0100
From:   Will Deacon <will@...nel.org>
To:     Qi Zheng <qi.zheng@...ux.dev>
Cc:     catalin.marinas@....com, akpm@...ux-foundation.org,
        wangkefeng.wang@...wei.co, pasha.tatashin@...een.com,
        muchun.song@...ux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH] arm64: mm: use ptep_clear() instead of pte_clear() in
 clear_flush()

On Thu, Aug 10, 2023 at 09:32:41AM +0000, Qi Zheng wrote:
> From: Qi Zheng <zhengqi.arch@...edance.com>
> 
> In clear_flush(), the original pte may be a present entry, so we should
> use ptep_clear() to let page_table_check track the pte clearing operation,
> otherwise it may cause false positive in subsequent set_pte_at().

Isn't this true for most users of pte_clear()? There are some in the core
code, so could they trigger the false positive as well?

Will