linux-kernel - Re: [PATCH v7 2/9] arm64: report address tag when FEAT_MTE_TAGGED

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Message-ID: <d93452bf-7296-47fc-9d48-44c390cb5080@sirena.org.uk>
Date: Wed, 11 Jun 2025 17:17:35 +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,
	yury.khrustalev@....com, maz@...nel.org, oliver.upton@...ux.dev,
	frederic@...nel.org, akpm@...ux-foundation.org, surenb@...gle.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v7 2/9] arm64: report address tag when
 FEAT_MTE_TAGGED_FAR is supported

On Wed, Jun 11, 2025 at 04:29:57PM +0100, Yeoreum Yun wrote:
> Hi Mark.
> > On Wed, Jun 11, 2025 at 02:58:11PM +0100, Yeoreum Yun wrote:

> > >  	 * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN
> > >  	 * for tag check faults. Set them to corresponding bits in the untagged
> > > -	 * address.
> > > +	 * address if ARM64_MTE_FAR isn't supported.
> > > +	 * Otherwise, bits 63:60 of FAR_EL1 are KNOWN.

> > Should that be "are UNKNOWN"?

> Otherwise in here mentions the case when ARM64_MTE_FAR is supported,
> So the bits 63:60 of FAR_EL1 are "not UNKNOWN" but I write it with
> KNOWN.

Ah, I see - KNOWN looks like one of the specially defined architectural
terms from the glossary of the ARM since it's all caps but KNOWN isn't
one of those words which was confusing me.

> Do you want to change this to "not UNKNOWN"?
> or Am I missing something?

DDI0487L.a D24.2.43 does use the term "not UNKNOWN" for that case so
that'd work like you suggest, or some other rewrite to use less formal
terms.  Like I say it was specifically the use of caps.

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