Re: [PATCH] arm64: kernel: Disable CNP on HiSilicon HIP09

[Vladimir Murzin <vladimir.murzin@arm.com>]

Hi,

On 5/26/26 02:57, Zeng Heng wrote:
> From: Tong Tiangen <tongtiangen@huawei.com>
> 
> HiSilicon HIP09 implements TLB entry matching behavior that deviates
> from the ARM architecture specification when the CNP (Common not Private)
> bit is set in TTBRx_ELx.
> 
> When TTBRx.CNP=1, TLB entries may be incorrectly shared between CPU
> cores, leading to TLB conflicts and stale mappings. This affects
> coherency and can result in incorrect translations.
> 
> Add the hardware erratum workaround (Hisilicon erratum 162100125) to
> disable CNP on affected HIP09 cores.
> 
> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
> Signed-off-by: Zeng Heng <zengheng4@huawei.com>
> ---
>  Documentation/arch/arm64/silicon-errata.rst |  2 ++
>  arch/arm64/Kconfig                          | 15 +++++++++++++++
>  arch/arm64/kernel/cpu_errata.c              |  7 +++++++
>  arch/arm64/kernel/cpufeature.c              |  3 ++-
>  arch/arm64/tools/cpucaps                    |  1 +
>  5 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
> index 211119ce7adc..cd50059edb85 100644
> --- a/Documentation/arch/arm64/silicon-errata.rst
> +++ b/Documentation/arch/arm64/silicon-errata.rst
> @@ -284,6 +284,8 @@ stable kernels.
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Hisilicon      | Hip09           | #162100801      | HISILICON_ERRATUM_162100801 |
>  +----------------+-----------------+-----------------+-----------------------------+
> +| Hisilicon      | Hip09           | #162100125      | HISILICON_ERRATUM_162100125 |
> ++----------------+-----------------+-----------------+-----------------------------+
>  +----------------+-----------------+-----------------+-----------------------------+
>  | Qualcomm Tech. | Kryo/Falkor v1  | E1003           | QCOM_FALKOR_ERRATUM_1003    |
>  +----------------+-----------------+-----------------+-----------------------------+
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fe60738e5943..ed6207c75b54 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1273,6 +1273,21 @@ config HISILICON_ERRATUM_162100801
>  
>  	  If unsure, say Y.
>  
> +config HISILICON_ERRATUM_162100125
> +	bool "Hisilicon erratum 162100125"
> +	default y
> +	help
> +	  On HiSilicon HIP09, TLB entry matching behavior when CNP
> +	  (TTBRx.CNP=1) is enabled differs from the ARM architecture
> +	  specification.
> +
> +	  TLB entries may be incorrectly shared between CPUs, potentially
> +	  causing TLB conflicts and stale mappings.
> +
> +	  Disable CNP support for affected HiSilicon HIP09 cores.
> +
> +	  If unsure, say Y.
> +
>  config QCOM_FALKOR_ERRATUM_1003
>  	bool "Falkor E1003: Incorrect translation due to ASID change"
>  	default y
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 5377e4c2eba2..26d9677a20fc 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -968,6 +968,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>  		.matches = has_impdef_pmuv3,
>  		.cpu_enable = cpu_enable_impdef_pmuv3_traps,
>  	},
> +#ifdef CONFIG_HISILICON_ERRATUM_162100125
> +	{
> +		.desc = "Hisilicon erratum 162100125",
> +		.capability = ARM64_WORKAROUND_HISILICON_ERRATUM_162100125,
> +		ERRATA_MIDR_ALL_VERSIONS(MIDR_HISI_HIP09),
> +	},
> +#endif
>  	{
>  	}
>  };
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 6d53bb15cf7b..c4b0db77a58a 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1785,7 +1785,8 @@ has_useable_cnp(const struct arm64_cpu_capabilities *entry, int scope)
>  	if (is_kdump_kernel())
>  		return false;
>  
> -	if (cpus_have_cap(ARM64_WORKAROUND_NVIDIA_CARMEL_CNP))
> +	if (cpus_have_cap(ARM64_WORKAROUND_NVIDIA_CARMEL_CNP) ||
> +	    cpus_have_cap(ARM64_WORKAROUND_HISILICON_ERRATUM_162100125))
>  		return false;

Since we now have a second user for this workaround, would it
make sense to:
1. factor out the existing ARM64_WORKAROUND_NVIDIA_CARMEL_CNP into a common capability,
   for example ARM64_WORKAROUND_DISABLE_CNP
2. wire up erratum 162100125 to use the common ARM64_WORKAROUND_DISABLE_CNP capability?

Cheers
Vladimir

>  
>  	return has_cpuid_feature(entry, scope);
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index 811c2479e82d..b797d4893adc 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -128,3 +128,4 @@ WORKAROUND_REPEAT_TLBI
>  WORKAROUND_SPECULATIVE_AT
>  WORKAROUND_SPECULATIVE_SSBS
>  WORKAROUND_SPECULATIVE_UNPRIV_LOAD
> +WORKAROUND_HISILICON_ERRATUM_162100125
> -- 2.43.0
>