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The AMU counter AMEVCNTR01 (constant counter) should increment at the same rate as the system counter. On affected Cortex-A510 cores, AMEVCNTR01 increments incorrectly giving a significantly higher output value. This results in inaccurate task scheduler utilization tracking and incorrect feedback on CPU frequency. Work around this problem by returning 0 when reading the affected counter in key locations that results in disabling all users of this counter from using it either for frequency invariance or as FFH reference counter. This effect is the same to firmware disabling affected counters. Details on how the two features are affected by this erratum: - AMU counters will not be used for frequency invariance for affected CPUs and CPUs in the same cpufreq policy. AMUs can still be used for frequency invariance for unaffected CPUs in the system. Although unlikely, if no alternative method can be found to support frequency invariance for affected CPUs (cpufreq based or solution based on platform counters) frequency invariance will be disabled. Please check the chapter on frequency invariance at Documentation/scheduler/sched-capacity.rst for details of its effect. - Given that FFH can be used to fetch either the core or constant counter values, restrictions are lifted regarding any of these counters returning a valid (!0) value. Therefore FFH is considered supported if there is a least one CPU that support AMUs, independent of any counters being disabled or affected by this erratum. Clarifying comments are now added to the cpc_ffh_supported(), cpu_read_constcnt() and cpu_read_corecnt() functions. The above is achieved through adding a new erratum: ARM64_ERRATUM_2457168. Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: James Morse <james.morse@arm.com> Link: https://lore.kernel.org/r/20220819103050.24211-1-ionela.voinescu@arm.com Signed-off-by: Will Deacon <will@kernel.org>
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=======================================
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Silicon Errata and Software Workarounds
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=======================================
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Author: Will Deacon <will.deacon@arm.com>
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Date : 27 November 2015
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It is an unfortunate fact of life that hardware is often produced with
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so-called "errata", which can cause it to deviate from the architecture
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under specific circumstances. For hardware produced by ARM, these
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errata are broadly classified into the following categories:
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========== ========================================================
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Category A A critical error without a viable workaround.
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Category B A significant or critical error with an acceptable
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workaround.
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Category C A minor error that is not expected to occur under normal
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operation.
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========== ========================================================
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For more information, consult one of the "Software Developers Errata
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Notice" documents available on infocenter.arm.com (registration
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required).
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As far as Linux is concerned, Category B errata may require some special
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treatment in the operating system. For example, avoiding a particular
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sequence of code, or configuring the processor in a particular way. A
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less common situation may require similar actions in order to declassify
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a Category A erratum into a Category C erratum. These are collectively
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known as "software workarounds" and are only required in the minority of
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cases (e.g. those cases that both require a non-secure workaround *and*
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can be triggered by Linux).
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For software workarounds that may adversely impact systems unaffected by
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the erratum in question, a Kconfig entry is added under "Kernel
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Features" -> "ARM errata workarounds via the alternatives framework".
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These are enabled by default and patched in at runtime when an affected
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CPU is detected. For less-intrusive workarounds, a Kconfig option is not
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available and the code is structured (preferably with a comment) in such
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a way that the erratum will not be hit.
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This approach can make it slightly onerous to determine exactly which
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errata are worked around in an arbitrary kernel source tree, so this
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file acts as a registry of software workarounds in the Linux Kernel and
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will be updated when new workarounds are committed and backported to
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stable kernels.
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+----------------+-----------------+-----------------+-----------------------------+
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| Implementor | Component | Erratum ID | Kconfig |
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+================+=================+=================+=============================+
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| Allwinner | A64/R18 | UNKNOWN1 | SUN50I_ERRATUM_UNKNOWN1 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2457168 | ARM64_ERRATUM_2457168 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2064142 | ARM64_ERRATUM_2064142 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2038923 | ARM64_ERRATUM_2038923 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #1902691 | ARM64_ERRATUM_1902691 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A55 | #1024718 | ARM64_ERRATUM_1024718 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A55 | #1530923 | ARM64_ERRATUM_1530923 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A57 | #852523 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A57 | #1319537 | ARM64_ERRATUM_1319367 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A57 | #1742098 | ARM64_ERRATUM_1742098 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A72 | #853709 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A72 | #1319367 | ARM64_ERRATUM_1319367 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A72 | #1655431 | ARM64_ERRATUM_1742098 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A73 | #858921 | ARM64_ERRATUM_858921 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A76 | #1188873,1418040| ARM64_ERRATUM_1418040 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A76 | #1165522 | ARM64_ERRATUM_1165522 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A76 | #1286807 | ARM64_ERRATUM_1286807 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A76 | #1463225 | ARM64_ERRATUM_1463225 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A77 | #1508412 | ARM64_ERRATUM_1508412 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2051678 | ARM64_ERRATUM_2051678 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2077057 | ARM64_ERRATUM_2077057 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2441009 | ARM64_ERRATUM_2441009 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A710 | #2119858 | ARM64_ERRATUM_2119858 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A710 | #2054223 | ARM64_ERRATUM_2054223 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A710 | #2224489 | ARM64_ERRATUM_2224489 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-X2 | #2119858 | ARM64_ERRATUM_2119858 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-X2 | #2224489 | ARM64_ERRATUM_2224489 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N1 | #1188873,1418040| ARM64_ERRATUM_1418040 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N1 | #1349291 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N1 | #1542419 | ARM64_ERRATUM_1542419 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N2 | #2139208 | ARM64_ERRATUM_2139208 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N2 | #2067961 | ARM64_ERRATUM_2067961 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Neoverse-N2 | #2253138 | ARM64_ERRATUM_2253138 |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | MMU-500 | #841119,826419 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_845719 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Broadcom | Brahma-B53 | N/A | ARM64_ERRATUM_843419 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX ITS | #22375,24313 | CAVIUM_ERRATUM_22375 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX GICv3 | #23154,38545 | CAVIUM_ERRATUM_23154 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX GICv3 | #38539 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX Core | #30115 | CAVIUM_ERRATUM_30115 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX SMMUv2 | #27704 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX2 SMMUv3| #74 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX2 SMMUv3| #126 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Cavium | ThunderX2 Core | #219 | CAVIUM_TX2_ERRATUM_219 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Marvell | ARM-MMU-500 | #582743 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| NVIDIA | Carmel Core | N/A | NVIDIA_CARMEL_CNP_ERRATUM |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Hisilicon | Hip0{5,6,7} | #161010101 | HISILICON_ERRATUM_161010101 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Hisilicon | Hip0{6,7} | #161010701 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Hisilicon | Hip0{6,7} | #161010803 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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| Hisilicon | Hip07 | #161600802 | HISILICON_ERRATUM_161600802 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Hisilicon | Hip08 SMMU PMCG | #162001800 | N/A |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo/Falkor v1 | E1003 | QCOM_FALKOR_ERRATUM_1003 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo/Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | QDF2400 ITS | E0065 | QCOM_QDF2400_ERRATUM_0065 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Falkor v{1,2} | E1041 | QCOM_FALKOR_ERRATUM_1041 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo4xx Gold | N/A | ARM64_ERRATUM_1463225 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo4xx Gold | N/A | ARM64_ERRATUM_1418040 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo4xx Silver | N/A | ARM64_ERRATUM_1530923 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo4xx Silver | N/A | ARM64_ERRATUM_1024718 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Qualcomm Tech. | Kryo4xx Gold | N/A | ARM64_ERRATUM_1286807 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| Fujitsu | A64FX | E#010001 | FUJITSU_ERRATUM_010001 |
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+----------------+-----------------+-----------------+-----------------------------+
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