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

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Message-ID: <aEnD6VOsz8zlQA/7@e129823.arm.com>
Date: Wed, 11 Jun 2025 18:59:05 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Mark Brown <broonie@...nel.org>
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

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.

Sorry to make you confused. anyway I'll use the term with not UNKNOWN
then.

Thanks

--
Sincerely,
Yeoreum Yun