linux-kernel - Re: [PATCH v3 29/39] arm64: mte: Switch GCR

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Message-ID: <20200925123810.GL4846@gaia>
Date:   Fri, 25 Sep 2020 13:38:10 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and
 exit

On Fri, Sep 25, 2020 at 12:50:23PM +0100, Vincenzo Frascino wrote:
> On 9/25/20 12:34 PM, Catalin Marinas wrote:
> > On Fri, Sep 25, 2020 at 12:50:36AM +0200, Andrey Konovalov wrote:
> >> +	/*
> >> +	 * Calculate and set the exclude mask preserving
> >> +	 * the RRND (bit[16]) setting.
> >> +	 */
> >> +	mrs_s	\tmp2, SYS_GCR_EL1
> >> +	bfi	\tmp2, \tmp, #0, #16
> >> +	msr_s	SYS_GCR_EL1, \tmp2
> >> +	isb
> >> +1:
> >> +#endif
> >> +	.endm
> >> +
> >> +	.macro mte_set_kernel_gcr, tsk, tmp, tmp2
> > 
> > What's the point of a 'tsk' argument here?
> 
> It is unused. I kept the interface same in between kernel and user.
> I can either add a comment or remove it. Which one do you prefer?

Please remove it. Having the same interface is more confusing since you
have a single kernel gcr_excl but multiple user gcr_excl.

-- 
Catalin