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During a TLB invalidate sequence targeting the inner shareable domain, Falkor may prematurely complete the DSB before all loads and stores using the old translation are observed. Instruction fetches are not subject to the conditions of this erratum. If the original code sequence includes multiple TLB invalidate instructions followed by a single DSB, onle one of the TLB instructions needs to be repeated to work around this erratum. While the erratum only applies to cases in which the TLBI specifies the inner-shareable domain (*IS form of TLBI) and the DSB is ISH form or stronger (OSH, SYS), this changes applies the workaround overabundantly-- to local TLBI, DSB NSH sequences as well--for simplicity. Based on work by Shanker Donthineni <shankerd@codeaurora.org> Signed-off-by: Christopher Covington <cov@codeaurora.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
67 lines
3.8 KiB
Plaintext
67 lines
3.8 KiB
Plaintext
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 | 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. | Falkor v1 | E1009 | QCOM_FALKOR_ERRATUM_1009|
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