Re: [PATCH V2 3/7] arm64: errata: Add detection for TRBE invalid prohibited states

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 07/01/2022 01:10, Anshuman Khandual wrote:
> TRBE implementations affected by Arm erratum #2038923 might get TRBE into
> an inconsistent view on whether trace is prohibited within the CPU. As a
> result, the trace buffer or trace buffer state might be corrupted. This
> happens after TRBE buffer has been enabled by setting TRBLIMITR_EL1.E,
> followed by just a single context synchronization event before execution
> changes from a context, in which trace is prohibited to one where it isn't,
> or vice versa. In these mentioned conditions, the view of whether trace is
> prohibited is inconsistent between parts of the CPU, and the trace buffer
> or the trace buffer state might be corrupted. This adds a new errata
> ARM64_ERRATUM_2038923 in arm64 errata framework.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Suzuki Poulose <suzuki.poulose@arm.com>
> Cc: coresight@lists.linaro.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>   Documentation/arm64/silicon-errata.rst |  2 ++
>   arch/arm64/Kconfig                     | 23 +++++++++++++++++++++++
>   arch/arm64/kernel/cpu_errata.c         |  9 +++++++++
>   arch/arm64/tools/cpucaps               |  1 +
>   4 files changed, 35 insertions(+)
> 
> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
> index c9b30e6c2b6c..e0ef3e9a4b8b 100644
> --- a/Documentation/arm64/silicon-errata.rst
> +++ b/Documentation/arm64/silicon-errata.rst
> @@ -54,6 +54,8 @@ stable kernels.
>   +----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Cortex-A510     | #2064142        | ARM64_ERRATUM_2064142       |
>   +----------------+-----------------+-----------------+-----------------------------+
> +| ARM            | Cortex-A510     | #2038923        | ARM64_ERRATUM_2038923       |
> ++----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Cortex-A53      | #826319         | ARM64_ERRATUM_826319        |
>   +----------------+-----------------+-----------------+-----------------------------+
>   | ARM            | Cortex-A53      | #827319         | ARM64_ERRATUM_827319        |
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index e27ccfe9fa9c..188eae6ef28d 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -796,6 +796,29 @@ config ARM64_ERRATUM_2064142
>   
>   	  If unsure, say Y.
>   
> +config ARM64_ERRATUM_2038923
> +	bool "Cortex-A510: 2038923: workaround TRBE corruption with enable"
> +	depends on COMPILE_TEST # Until the CoreSight TRBE driver changes are in
> +	default y
> +	help
> +	  This option adds the workaround for ARM Cortex-A510 erratum 2038923.
> +
> +	  Affected Cortex-A510 core might cause an inconsistent view on whether trace is
> +	  prohibited within the CPU. As a result, the trace buffer or trace buffer state
> +	  might be corrupted. This happens after TRBE buffer has been enabled by setting
> +	  TRBLIMITR_EL1.E, followed by just a single context synchronization event before
> +	  execution changes from a context, in which trace is prohibited to one where it
> +	  isn't, or vice versa. In these mentioned conditions, the view of whether trace
> +	  is prohibited is inconsistent between parts of the CPU, and the trace buffer or
> +	  the trace buffer state might be corrupted.
> +
> +	  Work around this in the driver by preventing an inconsistent view of whether the
> +	  trace is prohibited or not based on TRBLIMITR_EL1.E by immediately following a
> +	  change to TRBLIMITR_EL1.E with at least one ISB instruction before an ERET, or
> +	  two ISB instructions if no ERET is to take place.
> +
> +	  If unsure, say Y.
> +
>   config CAVIUM_ERRATUM_22375
>   	bool "Cavium erratum 22375, 24313"
>   	default y
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index cbb7d5a9aee7..60b0c1f1d912 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -607,6 +607,15 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>   		ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 2)
>   	},
>   #endif
> +#ifdef CONFIG_ARM64_ERRATUM_2038923
> +	{
> +		.desc = "ARM erratum 2038923",
> +		.capability = ARM64_WORKAROUND_2038923,
> +
> +		/* Cortex-A510 r0p0 - r0p2 */
> +		ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 2)
> +	},
> +#endif
>   	{
>   	}
>   };
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index fca3cb329e1d..45a06d36d080 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -56,6 +56,7 @@ WORKAROUND_1463225
>   WORKAROUND_1508412
>   WORKAROUND_1542419
>   WORKAROUND_2064142
> +WORKAROUND_2038923
>   WORKAROUND_TRBE_OVERWRITE_FILL_MODE
>   WORKAROUND_TSB_FLUSH_FAILURE
>   WORKAROUND_TRBE_WRITE_OUT_OF_RANGE