linux-kernel - Re: [PATCH v2 10/17] arm64: Enable workaround for TRBE overwrite in FILL mode

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Message-ID: <8b23470b-da5c-c624-dc98-d30ab7c1be5d@arm.com>
Date:   Wed, 22 Sep 2021 12:53:00 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, maz@...nel.org,
        catalin.marinas@....com, mark.rutland@....com, james.morse@....com,
        leo.yan@...aro.org, mike.leach@...aro.org,
        mathieu.poirier@...aro.org, will@...nel.org, lcherian@...vell.com,
        coresight@...ts.linaro.org
Subject: Re: [PATCH v2 10/17] arm64: Enable workaround for TRBE overwrite in
 FILL mode



On 9/21/21 7:11 PM, Suzuki K Poulose wrote:
> Now that we have the work around implmented in the TRBE
> driver, add the Kconfig entries and document the errata.
> 
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Mike Leach <mike.leach@...aro.org>
> Cc: Leo Yan <leo.yan@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
>  Documentation/arm64/silicon-errata.rst |  4 +++
>  arch/arm64/Kconfig                     | 39 ++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
> index d410a47ffa57..2f99229d993c 100644
> --- a/Documentation/arm64/silicon-errata.rst
> +++ b/Documentation/arm64/silicon-errata.rst
> @@ -92,12 +92,16 @@ stable kernels.
>  +----------------+-----------------+-----------------+-----------------------------+
>  | ARM            | Cortex-A77      | #1508412        | ARM64_ERRATUM_1508412       |
>  +----------------+-----------------+-----------------+-----------------------------+
> +| ARM            | Cortex-A710     | #2119858        | ARM64_ERRATUM_2119858       |
> ++----------------+-----------------+-----------------+-----------------------------+
>  | ARM            | Neoverse-N1     | #1188873,1418040| ARM64_ERRATUM_1418040       |
>  +----------------+-----------------+-----------------+-----------------------------+
>  | ARM            | Neoverse-N1     | #1349291        | N/A                         |
>  +----------------+-----------------+-----------------+-----------------------------+
>  | ARM            | Neoverse-N1     | #1542419        | ARM64_ERRATUM_1542419       |
>  +----------------+-----------------+-----------------+-----------------------------+
> +| ARM            | Neoverse-N2     | #2139208        | ARM64_ERRATUM_2139208       |
> ++----------------+-----------------+-----------------+-----------------------------+
>  | ARM            | MMU-500         | #841119,826419  | N/A                         |
>  +----------------+-----------------+-----------------+-----------------------------+
>  +----------------+-----------------+-----------------+-----------------------------+
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 077f2ec4eeb2..eac4030322df 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -666,6 +666,45 @@ config ARM64_ERRATUM_1508412
>  
>  	  If unsure, say Y.
>  
> +config ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> +	bool
> +
> +config ARM64_ERRATUM_2119858
> +	bool "Cortex-A710: 2119858: workaround TRBE overwriting trace data in FILL mode"
> +	default y
> +	depends on CORESIGHT_TRBE
> +	select ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> +	help
> +	  This option adds the workaround for ARM Cortex-A710 erratum 2119858.
> +
> +	  Affected Cortex-A710 cores could overwrite upto 3 cache lines of trace
> +	  data at the base of the buffer (ponited by TRBASER_EL1) in FILL mode in
> +	  the event of a WRAP event.
> +
> +	  Work around the issue by always making sure we move the TRBPTR_EL1 by
> +	  256bytes before enabling the buffer and filling the first 256bytes of
> +	  the buffer with ETM ignore packets upon disabling.
> +
> +	  If unsure, say Y.
> +
> +config ARM64_ERRATUM_2139208
> +	bool "Neoverse-N2: 2139208: workaround TRBE overwriting trace data in FILL mode"
> +	default y
> +	depends on CORESIGHT_TRBE
> +	select ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> +	help
> +	  This option adds the workaround for ARM Neoverse-N2 erratum 2139208.
> +
> +	  Affected Neoverse-N2 cores could overwrite upto 3 cache lines of trace
> +	  data at the base of the buffer (ponited by TRBASER_EL1) in FILL mode in

s/ponited/pointed

> +	  the event of a WRAP event.
> +
> +	  Work around the issue by always making sure we move the TRBPTR_EL1 by
> +	  256bytes before enabling the buffer and filling the first 256bytes of
> +	  the buffer with ETM ignore packets upon disabling.
> +
> +	  If unsure, say Y.
> +
>  config CAVIUM_ERRATUM_22375
>  	bool "Cavium erratum 22375, 24313"
>  	default y
> 

The real errata problem description for both these erratums are exactly
the same. Rather a more generalized description should be included for
the ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE, which abstracts out the
problem and a corresponding solution that is implemented in the driver.
This should also help us reduce current redundancy.

----------------------------------------------------------------------
Affected cores could overwrite upto 3 cache lines of trace data at the
base of the buffer (pointed by TRBASER_EL1) in FILL mode in the event
of a WRAP event.

Work around the issue by always making sure we move the TRBPTR_EL1 by
256bytes before enabling the buffer and filling the first 256bytes of
the buffer with ETM ignore packets upon disabling.
----------------------------------------------------------------------