linux-kernel - Re: [PATCH v3 3/4] arm64/kernel: support store-only mte tag check

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Message-ID: <aBUF6JduwlhHVR9E@arm.com>
Date: Fri, 2 May 2025 18:50:32 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: will@...nel.org, broonie@...nel.org, anshuman.khandual@....com,
	joey.gouly@....com, maz@...nel.org, oliver.upton@...ux.dev,
	frederic@...nel.org, james.morse@....com,
	hardevsinh.palaniya@...iconsignals.io,
	shameerali.kolothum.thodi@...wei.com, huangxiaojia2@...wei.com,
	mark.rutland@....com, 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, nd@....com,
	Peter Collingbourne <pcc@...gle.com>
Subject: Re: [PATCH v3 3/4] arm64/kernel: support store-only mte tag check

On Thu, Apr 10, 2025 at 09:07:22AM +0100, Yeoreum Yun wrote:
> Introduce new flag -- MTE_CTRL_STORE_ONLY used to set store-only tag check.
> This flag isn't overrided by prefered tcf flag setting but set together

Nit: s/overrided/overridden/

> with prefered setting of way to report tag check fault.

The preferred mode set via sysfs is about whether we want synchronous or
asynchronous tag check faults for reads/writes (or asymmetric). The
store-only checking can be combined with sync/async, so they are
slightly complementary. The question is whether one wants some global
knob to turn on store-only in combination with sync/async. We could add
more strings for sysfs like "(a)sync+storeonly"

It would be good to hear Peter's opinion from an Android perspective.

-- 
Catalin