69 lines
4.1 KiB
Plaintext
69 lines
4.1 KiB
Plaintext
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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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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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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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| Implementor | Component | Erratum ID | Kconfig |
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
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| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
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| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
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| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
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| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
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| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
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| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
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| ARM | Cortex-A57 | #852523 | N/A |
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| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
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| ARM | Cortex-A72 | #853709 | N/A |
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| ARM | Cortex-A55 | #1024718 | ARM64_ERRATUM_1024718 |
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| ARM | MMU-500 | #841119,#826419 | N/A |
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| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
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| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
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| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
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| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
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| Cavium | ThunderX SMMUv2 | #27704 | N/A |
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| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
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| Qualcomm Tech. | QDF2400 ITS | E0065 | QCOM_QDF2400_ERRATUM_0065 |
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