linux-kernel - Re: [PATCH v3 0/1] arm64: Add workaround for Fujitsu A64FX erratum 010001

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Message-ID: <20190201105144.GA27140@fuggles.cambridge.arm.com>
Date:   Fri, 1 Feb 2019 10:51:44 +0000
From:   Will Deacon <will.deacon@....com>
To:     "Zhang, Lei" <zhang.lei@...fujitsu.com>
Cc:     'James Morse' <james.morse@....com>,
        'Mark Rutland' <mark.rutland@....com>,
        'Catalin Marinas' <catalin.marinas@....com>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        "'linux-arm-kernel@...ts.infradead.org'" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 0/1] arm64: Add workaround for Fujitsu A64FX erratum
 010001

On Fri, Feb 01, 2019 at 05:53:50AM +0000, Zhang, Lei wrote:
> > -----Original Message-----
> > From: linux-arm-kernel
> > [mailto:linux-arm-kernel-bounces@...ts.infradead.org] On Behalf Of
> > James Morse
> > Sent: Thursday, January 31, 2019 12:00 AM
> > To: Zhang, Lei/張 雷
> > Cc: 'Mark Rutland'; 'Catalin Marinas'; 'will.deacon@....com';
> > 'linux-kernel@...r.kernel.org';
> > 'linux-arm-kernel@...ts.infradead.org'
> > Subject: Re: [PATCH v3 0/1] arm64: Add workaround for Fujitsu A64FX
> > erratum 010001
> > 
> > 
> > e03e61c3173c ("arm64: kaslr: Set TCR_EL1.NFD1 when
> > CONFIG_RANDOMIZE_BASE=y") ?
> > 
> > So you'd never see it if you disabled CONFIG_RANDOMIZE_BASE?
> For security, it is necessary to set CONFIG_RANDOMIZE_BASE=y.

So I guess we should boot with NFD1 clear, and then set it only when we
realise we're not on an A64FX?

Will