linux-kernel - Re: [PATCH 07/10] arm64: Add erratum detection for TRBE overwrite in FILL mode

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Date:   Mon, 2 Aug 2021 13:14:13 +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, coresight@...ts.linaro.org,
        will@...nel.org, catalin.marinas@....com, james.morse@....com,
        mathieu.poirier@...aro.org, mike.leach@...aro.org,
        leo.yan@...aro.org, maz@...nel.org, mark.rutland@....com
Subject: Re: [PATCH 07/10] arm64: Add erratum detection for TRBE overwrite in
 FILL mode



On 7/28/21 7:22 PM, Suzuki K Poulose wrote:
> Arm Neoverse-N2 and the Cortex-A710 cores are affected
> by a CPU erratum where the TRBE will overwrite the trace buffer
> in FILL mode. The TRBE doesn't stop (as expected in FILL mode)
> when it reaches the limit and wraps to the base to continue
> writing upto 3 cache lines. This will overwrite any trace that
> was written previously.
> 
> Add the Neoverse-N2 erratumi(#2139208) and Cortex-A710 erratum

Small nit. Stray 'i' here  ^^^^

> (#2119858) to the  detection logic.
> 
> This will be used by the TRBE driver in later patches to work
> around the issue. The detection has been kept with the core
> arm64 errata framework list to make sure :
>   - We don't duplicate the framework in TRBE driver
>   - The errata detection is advertised like the rest
>     of the CPU errata.
> 
> Note that the Kconfig entries will be added after we have added
> the work around in the TRBE driver, which depends on the cpucap
> from here.
> 
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Catalin Marinas <catalin.marinas@....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>
> ---
>  arch/arm64/kernel/cpu_errata.c | 25 +++++++++++++++++++++++++
>  arch/arm64/tools/cpucaps       |  1 +
>  2 files changed, 26 insertions(+)
> 
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index e2c20c036442..ccd757373f36 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -340,6 +340,18 @@ static const struct midr_range erratum_1463225[] = {
>  };
>  #endif
>  
> +#ifdef CONFIG_ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> +static const struct midr_range trbe_overwrite_fill_mode_cpus[] = {
> +#ifdef CONFIG_ARM64_ERRATUM_2139208
> +	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
> +#endif
> +#ifdef CONFIG_ARM64_ERRATUM_2119858
> +	MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
> +#endif
> +	{},
> +};
> +#endif	/* CONFIG_ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE */
> +
>  const struct arm64_cpu_capabilities arm64_errata[] = {
>  #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
>  	{
> @@ -533,6 +545,19 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>  		.capability = ARM64_WORKAROUND_NVIDIA_CARMEL_CNP,
>  		ERRATA_MIDR_ALL_VERSIONS(MIDR_NVIDIA_CARMEL),
>  	},
> +#endif
> +#ifdef CONFIG_ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> +	{
> +		/*
> +		 * The erratum work around is handled within the TRBE
> +		 * driver and can be applied per-cpu. So, we can allow
> +		 * a late CPU to come online with this erratum.
> +		 */
> +		.desc = "ARM erratum 2119858 or 2139208",
> +		.capability = ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE,
> +		.type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
> +		CAP_MIDR_RANGE_LIST(trbe_overwrite_fill_mode_cpus),
> +	},
>  #endif
>  	{
>  	}
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index 49305c2e6dfd..1ccb92165bd8 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -53,6 +53,7 @@ WORKAROUND_1418040
>  WORKAROUND_1463225
>  WORKAROUND_1508412
>  WORKAROUND_1542419
> +WORKAROUND_TRBE_OVERWRITE_FILL_MODE
>  WORKAROUND_CAVIUM_23154
>  WORKAROUND_CAVIUM_27456
>  WORKAROUND_CAVIUM_30115
> 

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>