linux-kernel - RE: [RESEND PATCH] Make Fujitsu Erratum 010001 patch can be applied on A64FX v1r0

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Date:   Mon, 18 Mar 2019 03:05:09 +0000
From:   "Zhang, Lei" <zhang.lei@...fujitsu.com>
To:     'Mark Rutland' <mark.rutland@....com>,
        "Okamoto, Takayuki" <tokamoto@...fujitsu.com>
CC:     'Catalin Marinas' <catalin.marinas@....com>,
        'Will Deacon' <will.deacon@....com>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        'James Morse' <james.morse@....com>,
        "'linux-arm-kernel@...ts.infradead.org'" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [RESEND PATCH] Make Fujitsu Erratum 010001 patch can be applied
 on A64FX v1r0

Hi guys,

> -----Original Message-----
> From: linux-arm-kernel <linux-arm-kernel-bounces@...ts.infradead.org> On
> Behalf Of Mark Rutland
> Sent: Saturday, March 16, 2019 12:13 AM
> To: Okamoto, Takayuki/岡本 高幸 <tokamoto@...fujitsu.com>
> Cc: 'Catalin Marinas' <catalin.marinas@....com>; 'Will Deacon'
> <will.deacon@....com>; 'linux-kernel@...r.kernel.org'
> <linux-kernel@...r.kernel.org>; Zhang, Lei/張 雷 <zhang.lei@...fujitsu.com>;
> 'James Morse' <james.morse@....com>; hange-folder>?
> <toggle-mailboxes@...rids.cambridge.arm.com>;
> 'linux-arm-kernel@...ts.infradead.org' <linux-arm-kernel@...ts.infradead.org>
> Subject: Re: [RESEND PATCH] Make Fujitsu Erratum 010001 patch can be
> applied on A64FX v1r0
> 
> On Fri, Mar 15, 2019 at 12:22:36PM +0000, Okamoto, Takayuki wrote:
> > I resend the patch due to whitespace munging.
> >
> > > -----Original Message-----
> > > From: James Morse <james.morse@....com>
> > > Sent: Wednesday, February 27, 2019 3:44 AM
> > > To: james.morse@....com; linux-arm-kernel@...ts.infradead.org
> > > Cc: linux-kernel@...r.kernel.org; Catalin Marinas
> > > <catalin.marinas@....com>; Mark Rutland <mark.rutland@....com>; Will
> > > Deacon <will.deacon@....com>; Zhang, Lei <zhang.lei@...fujitsu.com>
> > > Subject: [PATCH v5] arm64: Add workaround for Fujitsu A64FX erratum
> > > 010001
> > >
> > > +/* Fujitsu Erratum 010001 affects A64FX 1.0 and 1.1, (v0r0 and
> > > +v1r0) */ #define MIDR_FUJITSU_ERRATUM_010001
> > > 	MIDR_FUJITSU_A64FX
> > > +#define MIDR_FUJITSU_ERRATUM_010001_MASK
> > > 	(~MIDR_VARIANT(1))
> >
> > This workaround for the erratum should be applied for both A64FX v1r0
> > and v0r0, however, the patch v5 is only enabled on A64FX
> > v0r0(MIDR.Variant == 0 && MIDR.Revision == 0).
> > This issue is caused by the macro MIDR_FUJITSU_ERRATUM_010001_MASK.
> >
> > I have tested on both A64FX v1r0 and v0r0. This new patch will effect
> > only for A64FX.
> >
> > --
> > Changed to be applied for not only A64FX v0r0 but also v1r0.
> >
> > Signed-off-by: Zhang Lei <zhang.lei@...fujitsu.com>
> > ---
> >  arch/arm64/include/asm/cputype.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/include/asm/cputype.h
> > b/arch/arm64/include/asm/cputype.h
> > index 2afb133..1fb47b5 100644
> > --- a/arch/arm64/include/asm/cputype.h
> > +++ b/arch/arm64/include/asm/cputype.h
> > @@ -129,7 +129,7 @@
> >
> >  /* Fujitsu Erratum 010001 affects A64FX 1.0 and 1.1, (v0r0 and v1r0) */
> >  #define MIDR_FUJITSU_ERRATUM_010001
> 	MIDR_FUJITSU_A64FX
> > -#define MIDR_FUJITSU_ERRATUM_010001_MASK
> 	(~MIDR_VARIANT(1))
> 
> The bug is is that MIDR_VARIANT() is meant to extract the variant from a full
> MIDR value, not generate an in-place field value.
> 
> > +#define MIDR_FUJITSU_ERRATUM_010001_MASK	(~(0x1 <<
> MIDR_VARIANT_SHIFT))
> 
> I beleive this can be:
> 
> #define MIDR_FUJITSU_ERRATUM_010001_MASK	(~MIDR_VAR_REV(1,
> 0))

Thanks for your comments.
I also have considered to use MIDR_CPU_VAR_REV macro,
but the implication of (~MIDR_CPU_VAR_REV(1, 0)) is "NOT v1r0".
I think it may cause confusion, so I choose the
simple way (~(0x1 << MIDR_VARIANT_SHIFT)).

> But otherwise this looks fine to me.

Will this patch be merged to v5.1?

Thanks,
Zhang Lei