From: Rob Herring <robh@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
Marc Zyngier <maz@kernel.org>,
kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v2 3/3] arm64: Add workaround for Arm Cortex-A77 erratum 1508412
Date: Thu, 2 Jul 2020 08:56:05 -0600 [thread overview]
Message-ID: <CAL_JsqJRMvmx3pOgoQ0eiaTCcDCC1fbxJDv81uAXrUWpAaF2Tg@mail.gmail.com> (raw)
In-Reply-To: <20200702114218.GA16499@willie-the-truck>
On Thu, Jul 2, 2020 at 5:42 AM Will Deacon <will@kernel.org> wrote:
>
> On Wed, Jul 01, 2020 at 03:53:08PM -0600, Rob Herring wrote:
> > On Cortex-A77 r0p0 and r1p0, a sequence of a non-cacheable or device load
> > and a store exclusive or PAR_EL1 read can cause a deadlock.
> >
> > The workaround requires a DMB SY before and after a PAR_EL1 register read
> > and the disabling of KVM. KVM must be disabled to prevent the problematic
> > sequence in guests' EL1. This workaround also depends on a firmware
> > counterpart to enable the h/w to insert DMB SY after load and store
> > exclusive instructions. See the errata document SDEN-1152370 v10 [1] for
> > more information.
>
> This ^^ is out of date not that we're not disabling KVM.
Indeed, I fixed the kconfig text, but missed this.
> > All the other PAR_EL1 reads besides the one in
> > is_spurious_el1_translation_fault() are in KVM code, so the work-around is
> > not needed for them.
>
> And I think this now needs some extra work.
Ugg, that was too easy...
The KVM code in __translate_far_to_hpfar() has:
read PAR
read PAR
write PAR
I'm wondering if we need 2 dmbs or 4 here. I'm checking on that.
Rob
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next prev parent reply other threads:[~2020-07-02 14:56 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 21:53 [PATCH v2 0/3] Cortex-A77 erratum 1508412 work-around Rob Herring
2020-07-01 21:53 ` [PATCH v2 1/3] KVM: arm64: Print warning when cpu erratum can cause guests to deadlock Rob Herring
2020-07-02 11:45 ` Will Deacon
2020-07-02 14:04 ` Rob Herring
2020-07-02 14:42 ` Will Deacon
2020-07-01 21:53 ` [PATCH v2 2/3] arm64: Add part number for Arm Cortex-A77 Rob Herring
2020-07-01 21:53 ` [PATCH v2 3/3] arm64: Add workaround for Arm Cortex-A77 erratum 1508412 Rob Herring
2020-07-02 11:42 ` Will Deacon
2020-07-02 14:56 ` Rob Herring [this message]
2020-07-02 15:01 ` Will Deacon
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