linux-kernel - Re: [PATCH v3 04/23] arm64: Move MAIR_EL1

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Message-ID: <20201201135839.jsvplmeodjzsa4he@google.com>
Date:   Tue, 1 Dec 2020 13:58:39 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     kvmarm@...ts.cs.columbia.edu, Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 04/23] arm64: Move MAIR_EL1_SET to asm/memory.h

Hey Mark,

> > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
> > index cd61239bae8c..54a22cb5b17b 100644
> > --- a/arch/arm64/include/asm/memory.h
> > +++ b/arch/arm64/include/asm/memory.h
> > @@ -152,6 +152,19 @@
> >  #define MT_S2_FWB_NORMAL	6
> >  #define MT_S2_FWB_DEVICE_nGnRE	1
> >  
> > +/*
> > + * Default MAIR_ELx. MT_NORMAL_TAGGED is initially mapped as Normal memory and
> > + * changed during __cpu_setup to Normal Tagged if the system supports MTE.
> > + */
> > +#define MAIR_ELx_SET							\
> > +	(MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRnE) |	\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRE, MT_DEVICE_nGnRE) |	\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_DEVICE_GRE, MT_DEVICE_GRE) |		\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_NORMAL_NC, MT_NORMAL_NC) |		\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL) |			\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_NORMAL_WT, MT_NORMAL_WT) |		\
> > +	 MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL_TAGGED))
> 
> Patch 7 initializes MAIR_EL2 with this directly rather than copying it
> from MAIR_EL1, which means that MT_NORMAL_TAGGED will never be tagged
> within the nVHE hyp code.
> 
> Is that expected? I suspect it's worth a comment here (introduced in
> patch 7), just to make that clear.

Ouch, that didn't use to be there. In that case let's not build more implicit
assumptions into the code. I'll pass MAIR_EL1 in kvm_nvhe_init_params.

David