linux-kernel - Re: [PATCH v2] arm64: cpu_errata: Add Kryo to Falkor 1003 errata

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Date:   Wed, 13 Dec 2017 13:31:08 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Will Deacon <will.deacon@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] arm64: cpu_errata: Add Kryo to Falkor 1003 errata

On 12/12, Will Deacon wrote:
> Hi Stephen,
> 
> On Wed, Nov 29, 2017 at 03:03:53PM -0800, Stephen Boyd wrote:
> > The Kryo CPUs are also affected by the Falkor 1003 errata, so
> > we need to do the same workaround on Kryo CPUs. The MIDR is
> > slightly more complicated here, where the PART number is not
> > always the same when looking at all the bits from 15 to 4. Drop
> > the lower 8 bits and just look at the top 4 to see if it's '2'
> > and then consider those as Kryo CPUs. This covers all the
> > combinations without having to list them all out.
> > 
> > Introduce a new hardware cap bit for the combination of hardware
> > PAN support and this errata so that we can disable support for
> > software PAN at runtime if this errata is present and the CPU
> > doesn't support HW PAN. This happens on some Kryo CPUs where the
> > HW PAN feature isn't supported but we can't prevent software PAN
> > from being selected in the configuration. Previously, Falkor CPUs
> > were all known to have HW PAN support, so we didn't need to worry
> > about this case.
> > 
> > Fixes: 38fd94b0275c ("arm64: Work around Falkor erratum 1003")
> > Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> > ---
> 
> Can you respin this on top of for-next/core please? The PAN bits should
> be much simpler with the KPTI code.
> 

No problem. I'll send it out in a couple hours.

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