Re: [PATCH v2] arm64: kernel: Unify CNP disable workaround into ARM64_WORKAROUND_DISABLE_CNP
From: Vladimir Murzin
Date: Fri May 29 2026 - 05:21:23 EST
Hi,
On 5/29/26 07:31, Zeng Heng wrote:
> From: Zeng Heng <zengheng4@xxxxxxxxxx>
>
> 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 breaks
> coherency and can result in incorrect translations.
>
> Add the hardware erratum workaround (Hisilicon erratum 162100125) to
> disable CNP on affected HIP09 cores.
>
> Merge the existing NVIDIA Carmel and the HiSilicon HIP09 CNP errata
> workarounds into a single generic capability ARM64_WORKAROUND_DISABLE_CNP.
>
> Both NVIDIA Carmel and HiSilicon HIP09 have hardware errata where
> CNP (Common Not Private) behavior differs from the ARM specification,
> causing incorrect TLB entry sharing between cores. The existing
> NVIDIA_CARMEL_CNP_ERRATUM and the newly added HISILICON_ERRATUM_162100125
> are now both handled by the unified ARM64_WORKAROUND_DISABLE_CNP.
>
> Co-developed-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> Signed-off-by: Zeng Heng <zengheng4@xxxxxxxxxx>
> ---
> v1: https://lore.kernel.org/all/20260526015720.206854-1-zengheng@xxxxxxxxxxxxxxx/
>
> Changes in v2:
> - Unify CNP disable workaround into ARM64_WORKAROUND_DISABLE_CNP
> ---
>
> Documentation/arch/arm64/silicon-errata.rst | 4 +++-
> arch/arm64/Kconfig | 17 ++++++++++++-----
> arch/arm64/include/asm/cpucaps.h | 4 ++--
> arch/arm64/kernel/cpu_errata.c | 17 ++++++++++++-----
> arch/arm64/kernel/cpufeature.c | 2 +-
> arch/arm64/tools/cpucaps | 2 +-
> 6 files changed, 31 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
> index 211119ce7adc..b4565e1a726d 100644
> --- a/Documentation/arch/arm64/silicon-errata.rst
> +++ b/Documentation/arch/arm64/silicon-errata.rst
> @@ -254,7 +254,7 @@ stable kernels.
> | Marvell | ARM-MMU-500 | #582743 | N/A |
> +----------------+-----------------+-----------------+-----------------------------+
> +----------------+-----------------+-----------------+-----------------------------+
> -| NVIDIA | Carmel Core | N/A | NVIDIA_CARMEL_CNP_ERRATUM |
> +| NVIDIA | Carmel Core | N/A | ARM64_WORKAROUND_DISABLE_CNP|
> +----------------+-----------------+-----------------+-----------------------------+
> | NVIDIA | T241 GICv3/4.x | T241-FABRIC-4 | N/A |
> +----------------+-----------------+-----------------+-----------------------------+
> @@ -284,6 +284,8 @@ stable kernels.
> +----------------+-----------------+-----------------+-----------------------------+
> | Hisilicon | Hip09 | #162100801 | HISILICON_ERRATUM_162100801 |
> +----------------+-----------------+-----------------+-----------------------------+
> +| Hisilicon | Hip09 | #162100125 | ARM64_WORKAROUND_DISABLE_CNP|
> ++----------------+-----------------+-----------------+-----------------------------+
> +----------------+-----------------+-----------------+-----------------------------+
> | Qualcomm Tech. | Kryo/Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
> +----------------+-----------------+-----------------+-----------------------------+
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index fe60738e5943..dc0bd32ea2d1 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1315,13 +1315,20 @@ config QCOM_FALKOR_ERRATUM_E1041
>
> If unsure, say Y.
>
> -config NVIDIA_CARMEL_CNP_ERRATUM
> - bool "NVIDIA Carmel CNP: CNP on Carmel semantically different than ARM cores"
> +config ARM64_WORKAROUND_DISABLE_CNP
> + bool "Disable CNP on affected CPUs"
> default y
> help
> - If CNP is enabled on Carmel cores, non-sharable TLBIs on a core will not
> - invalidate shared TLB entries installed by a different core, as it would
> - on standard ARM cores.
> + This option disables the CNP (Common Not Private) feature on CPUs
> + that have hardware errata affecting CNP behavior.
> +
> + On NVIDIA Carmel cores, CNP behaves differently than on standard ARM
> + cores: non-shareable TLBIs on a core may not invalidate shared TLB
> + entries installed by a different core.
> +
> + On Hisilicon HIP09 cores, TLB entries may be incorrectly shared
> + between cores when TTBRx.CNP=1, leading to TLB conflicts and
> + stale mappings.
>
> If unsure, say Y.
>
I'm afraid we cannot swap one config with another. Instead, we need to follow
established pattern for sharing workaround, something like
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 378e50fef247..68eb2993cfd3 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1315,9 +1315,13 @@ config QCOM_FALKOR_ERRATUM_E1041
If unsure, say Y.
+config ARM64_WORKAROUND_DISABLE_CNP
+ bool
+
config NVIDIA_CARMEL_CNP_ERRATUM
bool "NVIDIA Carmel CNP: CNP on Carmel semantically different than ARM cores"
default y
+ select ARM64_WORKAROUND_DISABLE_CNP
help
If CNP is enabled on Carmel cores, non-sharable TLBIs on a core will not
invalidate shared TLB entries installed by a different core, as it would
and related changes for generalisation of the workaround - that would to be patch 1/2.
Then we can easily wire-up your errata with something like
+config HISILICON_ERRATUM_162100125
+ bool "Hisilicon erratum 162100125"
+ default y
+ select ARM64_WORKAROUND_DISABLE_CNP
+ 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.
and related update in documentation and MIDR list - that would be patch 2/2
Thanks
Vladimir
> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
> index d0d3cdd5763c..25c61cda901c 100644
> --- a/arch/arm64/include/asm/cpucaps.h
> +++ b/arch/arm64/include/asm/cpucaps.h
> @@ -58,8 +58,8 @@ cpucap_is_possible(const unsigned int cap)
> return IS_ENABLED(CONFIG_ARM64_ERRATUM_2658417);
> case ARM64_WORKAROUND_CAVIUM_23154:
> return IS_ENABLED(CONFIG_CAVIUM_ERRATUM_23154);
> - case ARM64_WORKAROUND_NVIDIA_CARMEL_CNP:
> - return IS_ENABLED(CONFIG_NVIDIA_CARMEL_CNP_ERRATUM);
> + case ARM64_WORKAROUND_DISABLE_CNP:
> + return IS_ENABLED(CONFIG_ARM64_WORKAROUND_DISABLE_CNP);
> case ARM64_WORKAROUND_REPEAT_TLBI:
> return IS_ENABLED(CONFIG_ARM64_WORKAROUND_REPEAT_TLBI);
> case ARM64_WORKAROUND_SPECULATIVE_SSBS:
> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
> index 5377e4c2eba2..675cd059165c 100644
> --- a/arch/arm64/kernel/cpu_errata.c
> +++ b/arch/arm64/kernel/cpu_errata.c
> @@ -394,6 +394,14 @@ static const struct arm64_cpu_capabilities qcom_erratum_1003_list[] = {
> };
> #endif
>
> +#ifdef CONFIG_ARM64_WORKAROUND_DISABLE_CNP
> +static const struct midr_range cnp_erratum_cpus[] = {
> + MIDR_ALL_VERSIONS(MIDR_NVIDIA_CARMEL),
> + MIDR_ALL_VERSIONS(MIDR_HISI_HIP09),
> + {},
> +};
> +#endif
> +
> #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
> static const struct midr_range workaround_clean_cache[] = {
> #if defined(CONFIG_ARM64_ERRATUM_826319) || \
> @@ -801,12 +809,11 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
> 1, 0),
> },
> #endif
> -#ifdef CONFIG_NVIDIA_CARMEL_CNP_ERRATUM
> +#ifdef CONFIG_ARM64_WORKAROUND_DISABLE_CNP
> {
> - /* NVIDIA Carmel */
> - .desc = "NVIDIA Carmel CNP erratum",
> - .capability = ARM64_WORKAROUND_NVIDIA_CARMEL_CNP,
> - ERRATA_MIDR_ALL_VERSIONS(MIDR_NVIDIA_CARMEL),
> + .desc = "NVIDIA Carmel CNP erratum, or Hisilicon erratum 162100125",
> + .capability = ARM64_WORKAROUND_DISABLE_CNP,
> + ERRATA_MIDR_RANGE_LIST(cnp_erratum_cpus),
> },
> #endif
> #ifdef CONFIG_ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 6d53bb15cf7b..20c5f24f74a9 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1785,7 +1785,7 @@ 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_DISABLE_CNP))
> return false;
>
> return has_cpuid_feature(entry, scope);
> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> index 811c2479e82d..9b85a84f6fd4 100644
> --- a/arch/arm64/tools/cpucaps
> +++ b/arch/arm64/tools/cpucaps
> @@ -120,7 +120,7 @@ WORKAROUND_CAVIUM_TX2_219_PRFM
> WORKAROUND_CAVIUM_TX2_219_TVM
> WORKAROUND_CLEAN_CACHE
> WORKAROUND_DEVICE_LOAD_ACQUIRE
> -WORKAROUND_NVIDIA_CARMEL_CNP
> +WORKAROUND_DISABLE_CNP
> WORKAROUND_PMUV3_IMPDEF_TRAPS
> WORKAROUND_QCOM_FALKOR_E1003
> WORKAROUND_QCOM_ORYON_CNTVOFF
> --
> 2.43.0
>