linux-kernel - Re: [PATCH v5 4/6] kselftest/arm64/mte: preparation for mtefar test

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Message-ID: <aEhRkDzankUBPQp2@e129823.arm.com>
Date: Tue, 10 Jun 2025 16:38:56 +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, shmeerali.kolothum.thodi@...wei.com,
	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 v5 4/6] kselftest/arm64/mte: preparation for mtefar test

Hi Mark,

> > If FEAT_MTE_TAGGED_FAR (Armv8.9) is supported, bits 63:60 of the fault address
> > are preserved in response to synchronous tag check faults (SEGV_MTESERR).
> >
> > This patch is preparation for testing FEAT_MTE_TAGGED_FAR.
> > It shouldn't change the test result.
>
> I'm not clear from the above what the change is intended to do (ie, how
> does it prepare for testing FEAT_MTE_TAGGED_FAR).  I think this could
> usefully be split out into multiple commits (eg, adding logging of the
> additional si_ fields separately, or splitting the renaming MT_CLEAR_TAG
> to MT_CLEAR_TAGS), it's kind of hard to review as is.

My bad. I'll split this one. Thanks

>
> > @@ -45,13 +64,18 @@ void mte_default_handler(int signum, siginfo_t *si, void *uc)
> >  		}
> >  		/* Compare the context for precise error */
> >  		else if (si->si_code == SEGV_MTESERR) {
> > +		 	if ((!mtefar_support && si_atag) || (si_atag != MT_FETCH_ATAG(cur_mte_cxt.trig_addr))) {
> > +			  ksft_print_msg("Invalid MTE synchronous exception caught for address tag! si_tag=%x, si_atag: %x\n", si_tag, si_atag);
> > +			  exit(1);
> > +			}
>
> We should really exit with a kselftest error rather than just a number,
> though I see this is just copying the existing style for the file so
> *shrug*.

Okay. I'll change this

--
Sincerely,
Yeoreum Yun