linux-kernel - Re: [PATCH v5 3/7] arm64/kernel: support store-only mte tag check

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Message-ID: <3a0ed679-dfb0-4b10-a081-db56583bffbe@sirena.org.uk>
Date: Wed, 11 Jun 2025 14:19:59 +0100
From: Mark Brown <broonie@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, pcc@...gle.com, will@...nel.org,
	anshuman.khandual@....com, joey.gouly@....com, maz@...nel.org,
	oliver.upton@...ux.dev, frederic@...nel.org,
	hardevsinh.palaniya@...iconsignals.io, samuel.holland@...ive.com,
	palmer@...osinc.com, charlie@...osinc.com,
	thiago.bauermann@...aro.org, bgray@...ux.ibm.com,
	tglx@...utronix.de, puranjay@...nel.org, david@...hat.com,
	yang@...amperecomputing.com, mbenes@...e.cz,
	joel.granados@...nel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/7] arm64/kernel: support store-only mte tag check

On Wed, Jun 11, 2025 at 10:47:58AM +0100, Yeoreum Yun wrote:

> Introduce new flag -- MTE_CTRL_STORE_ONLY used to set store-only tag check.
> This flag isn't overridden by prefered tcf flag setting but set together
> with prefered setting of way to report tag check fault.

There was a concern when adding asymmetric support that when adding new
prctl() bits might cause issues when libraries linked into a program
don't know about the new bits and miss enabling/disabling them.  That
doesn't seem such an issue here since unlike with asymmetric mode store
only mode doesn't turn MTE on or off entirely, it's more an
optimisation.  There's some possibility that something could rely on
only stores faulting but I'm struggling to think of a real use case.
Assuming that's OK:

Reviewed-by: Mark Brown <broonie@...nel.org>

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