linux-kernel - Re: [PATCH 1/2] arm64: Rename WORKAROUND_1165522 to SPECULATIVE

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Date:   Mon, 11 Nov 2019 16:51:41 +0109
From:   Marc Zyngier <maz@...nel.org>
To:     Steven Price <steven.price@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, <kvmarm@...ts.cs.columbia.edu>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: Re: [PATCH 1/2] arm64: Rename WORKAROUND_1165522 to SPECULATIVE_AT

Hi Steven,

On 2019-11-11 15:21, Steven Price wrote:
> Cortex-A55 is affected by a similar erratum, so rename the existing
> workaround for errarum 1165522 so it can be used for both errata.

nit: erratum

>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>  arch/arm64/Kconfig                |  4 ++++
>  arch/arm64/include/asm/cpucaps.h  |  2 +-
>  arch/arm64/include/asm/kvm_host.h |  2 +-
>  arch/arm64/include/asm/kvm_hyp.h  |  3 +--
>  arch/arm64/kernel/cpu_errata.c    | 17 +++++++++++++----
>  arch/arm64/kvm/hyp/switch.c       |  2 +-
>  arch/arm64/kvm/hyp/tlb.c          |  4 ++--
>  7 files changed, 23 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 3f047afb982c..6cb4eff602c6 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -510,9 +510,13 @@ config ARM64_ERRATUM_1418040
>
>  	  If unsure, say Y.
>
> +config ARM64_WORKAROUND_SPECULATIVE_AT
> +	bool
> +
>  config ARM64_ERRATUM_1165522
>  	bool "Cortex-A76: Speculative AT instruction using out-of-context
> translation regime could cause subsequent request to generate an
> incorrect translation"
>  	default y
> +	select ARM64_WORKAROUND_SPECULATIVE_AT

I'd object that ARM64_ERRATUM_1319367 (and its big brother 1319537)
are also related to speculative AT execution, and yet are not covered
by this configuration symbol.

I can see three solutions to this:

- Either you call it SPECULATIVE_AT_VHE and introduce 
SPECULATIVE_AT_NVHE
   for symmetry

- Or you make SPECULATIVE_AT cover all the speculative AT errata, which
   may or may not work...

- Or even better, you just ammend the documentation to say that 1165522
   also covers the newly found A55 one (just like we have for A57/A72)

What do you think?

         M.
-- 
Jazz is not dead. It just smells funny...