linux-kernel - Re: [PATCH v2 2/5] KVM: arm64: Support set the DBM attr during memory abort

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Message-ID: <86v7j2qlc8.wl-maz@kernel.org>
Date: Sat, 22 Nov 2025 12:54:15 +0000
From: Marc Zyngier <maz@...nel.org>
To: Tian Zheng <zhengtian10@...wei.com>
Cc: <oliver.upton@...ux.dev>,
	<catalin.marinas@....com>,
	<corbet@....net>,
	<pbonzini@...hat.com>,
	<will@...nel.org>,
	<linux-kernel@...r.kernel.org>,
	<yuzenghui@...wei.com>,
	<wangzhou1@...ilicon.com>,
	<yezhenyu2@...wei.com>,
	<xiexiangyou@...wei.com>,
	<zhengchuan@...wei.com>,
	<linuxarm@...wei.com>,
	<joey.gouly@....com>,
	<kvmarm@...ts.linux.dev>,
	<kvm@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-doc@...r.kernel.org>,
	<suzuki.poulose@....com>
Subject: Re: [PATCH v2 2/5] KVM: arm64: Support set the DBM attr during memory abort

On Fri, 21 Nov 2025 09:23:39 +0000,
Tian Zheng <zhengtian10@...wei.com> wrote:
> 
> From: eillon <yezhenyu2@...wei.com>
> 
> Add DBM support to automatically promote write-clean pages to
> write-dirty, preventing users from being trapped in EL2 due to
> missing write permissions.
> 
> Since the DBM attribute was introduced in ARMv8.1 and remains
> optional in later architecture revisions, including ARMv9.5.

What is the relevance of this statement?

> 
> Support set the DBM attr during user_mem_abort().

I don't think this commit message accurately describes what the code
does. This merely adds support to the page table code to set the DBM
bit in the S2 PTE, and nothing else.

	M.

-- 
Without deviation from the norm, progress is not possible.