linux-kernel - Re: [PATCH v3 3/3] arm64: Workaround for Cortex-A55 erratum 1530923

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Date:   Thu, 14 Nov 2019 10:27:31 +0000
From:   Suzuki Kuruppassery Poulose <suzuki.poulose@....com>
To:     Steven Price <steven.price@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>
Cc:     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>
Subject: Re: [PATCH v3 3/3] arm64: Workaround for Cortex-A55 erratum 1530923

On 13/11/2019 17:22, Steven Price wrote:
> Cortex-A55 erratum 1530923 allows TLB entries to be allocated as a
> result of a speculative AT instruction. This may happen in the middle of
> a guest world switch while the relevant VMSA configuration is in an
> inconsistent state, leading to erroneous content being allocated into
> TLBs.
> 
> The same workaround as is used for Cortex-A76 erratum 1165522
> (WORKAROUND_SPECULATIVE_AT_NVE) can be used here. Note that this
> mandates the use of VHE on affected parts.
> 
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>   Documentation/arm64/silicon-errata.rst |  2 ++
>   arch/arm64/Kconfig                     | 13 +++++++++++++
>   arch/arm64/include/asm/kvm_hyp.h       |  4 ++--
>   arch/arm64/kernel/cpu_errata.c         |  6 +++++-
>   arch/arm64/kvm/hyp/switch.c            |  4 ++--
>   arch/arm64/kvm/hyp/tlb.c               |  4 ++--
>   6 files changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
> index 899a72570282..b40cb3e0634e 100644
> --- a/Documentation/arm64/silicon-errata.rst
> +++ b/Documentation/arm64/silicon-errata.rst
> @@ -88,6 +88,8 @@ stable kernels.
>   +----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Cortex-A76      | #1463225        | ARM64_ERRATUM_1463225       |
>   +----------------+-----------------+-----------------+-----------------------------+
> +| ARM            | Cortex-A55      | #1530923        | ARM64_ERRATUM_1530923       |
> ++----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Neoverse-N1     | #1188873,1418040| ARM64_ERRATUM_1418040       |
>   +----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Neoverse-N1     | #1349291        | N/A                         |
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index defb68e45387..d2dd72c19560 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -532,6 +532,19 @@ config ARM64_ERRATUM_1165522
>   
>   	  If unsure, say Y.
>   
> +config ARM64_ERRATUM_1530923
> +	bool "Cortex-A55: 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

ARM64_WORKAROUND_SPECULATIVE_AT_VHE ?

Otherwise looks good to me.

Suzuki