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diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst new file mode 100644 index 00000000..d099ebe2 --- /dev/null +++ b/docs/design/cpu-specific-build-macros.rst @@ -0,0 +1,298 @@ +Arm CPU Specific Build Macros +============================= + + + + +.. contents:: + +This document describes the various build options present in the CPU specific +operations framework to enable errata workarounds and to enable optimizations +for a specific CPU on a platform. + +Security Vulnerability Workarounds +---------------------------------- + +TF-A exports a series of build flags which control which security +vulnerability workarounds should be applied at runtime. + +- ``WORKAROUND_CVE_2017_5715``: Enables the security workaround for + `CVE-2017-5715`_. This flag can be set to 0 by the platform if none + of the PEs in the system need the workaround. Setting this flag to 0 provides + no performance benefit for non-affected platforms, it just helps to comply + with the recommendation in the spec regarding workaround discovery. + Defaults to 1. + +- ``WORKAROUND_CVE_2018_3639``: Enables the security workaround for + `CVE-2018-3639`_. Defaults to 1. The TF-A project recommends to keep + the default value of 1 even on platforms that are unaffected by + CVE-2018-3639, in order to comply with the recommendation in the spec + regarding workaround discovery. + +- ``DYNAMIC_WORKAROUND_CVE_2018_3639``: Enables dynamic mitigation for + `CVE-2018-3639`_. This build option should be set to 1 if the target + platform contains at least 1 CPU that requires dynamic mitigation. + Defaults to 0. + +CPU Errata Workarounds +---------------------- + +TF-A exports a series of build flags which control the errata workarounds that +are applied to each CPU by the reset handler. The errata details can be found +in the CPU specific errata documents published by Arm: + +- `Cortex-A53 MPCore Software Developers Errata Notice`_ +- `Cortex-A57 MPCore Software Developers Errata Notice`_ +- `Cortex-A72 MPCore Software Developers Errata Notice`_ + +The errata workarounds are implemented for a particular revision or a set of +processor revisions. This is checked by the reset handler at runtime. Each +errata workaround is identified by its ``ID`` as specified in the processor's +errata notice document. The format of the define used to enable/disable the +errata workaround is ``ERRATA_<Processor name>_<ID>``, where the ``Processor name`` +is for example ``A57`` for the ``Cortex_A57`` CPU. + +Refer to the section *CPU errata status reporting* in +`Firmware Design guide`_ for information on how to write errata workaround +functions. + +All workarounds are disabled by default. The platform is responsible for +enabling these workarounds according to its requirement by defining the +errata workaround build flags in the platform specific makefile. In case +these workarounds are enabled for the wrong CPU revision then the errata +workaround is not applied. In the DEBUG build, this is indicated by +printing a warning to the crash console. + +In the current implementation, a platform which has more than 1 variant +with different revisions of a processor has no runtime mechanism available +for it to specify which errata workarounds should be enabled or not. + +The value of the build flags is 0 by default, that is, disabled. A value of 1 +will enable it. + +For Cortex-A9, the following errata build flags are defined : + +- ``ERRATA_A9_794073``: This applies errata 794073 workaround to Cortex-A9 + CPU. This needs to be enabled for all revisions of the CPU. + +For Cortex-A15, the following errata build flags are defined : + +- ``ERRATA_A15_816470``: This applies errata 816470 workaround to Cortex-A15 + CPU. This needs to be enabled only for revision >= r3p0 of the CPU. + +- ``ERRATA_A15_827671``: This applies errata 827671 workaround to Cortex-A15 + CPU. This needs to be enabled only for revision >= r3p0 of the CPU. + +For Cortex-A17, the following errata build flags are defined : + +- ``ERRATA_A17_852421``: This applies errata 852421 workaround to Cortex-A17 + CPU. This needs to be enabled only for revision <= r1p2 of the CPU. + +- ``ERRATA_A17_852423``: This applies errata 852423 workaround to Cortex-A17 + CPU. This needs to be enabled only for revision <= r1p2 of the CPU. + +For Cortex-A35, the following errata build flags are defined : + +- ``ERRATA_A35_855472``: This applies errata 855472 workaround to Cortex-A35 + CPUs. This needs to be enabled only for revision r0p0 of Cortex-A35. + +For Cortex-A53, the following errata build flags are defined : + +- ``ERRATA_A53_819472``: This applies errata 819472 workaround to all + CPUs. This needs to be enabled only for revision <= r0p1 of Cortex-A53. + +- ``ERRATA_A53_824069``: This applies errata 824069 workaround to all + CPUs. This needs to be enabled only for revision <= r0p2 of Cortex-A53. + +- ``ERRATA_A53_826319``: This applies errata 826319 workaround to Cortex-A53 + CPU. This needs to be enabled only for revision <= r0p2 of the CPU. + +- ``ERRATA_A53_827319``: This applies errata 827319 workaround to all + CPUs. This needs to be enabled only for revision <= r0p2 of Cortex-A53. + +- ``ERRATA_A53_835769``: This applies erratum 835769 workaround at compile and + link time to Cortex-A53 CPU. This needs to be enabled for some variants of + revision <= r0p4. This workaround can lead the linker to create ``*.stub`` + sections. + +- ``ERRATA_A53_836870``: This applies errata 836870 workaround to Cortex-A53 + CPU. This needs to be enabled only for revision <= r0p3 of the CPU. From + r0p4 and onwards, this errata is enabled by default in hardware. + +- ``ERRATA_A53_843419``: This applies erratum 843419 workaround at link time + to Cortex-A53 CPU. This needs to be enabled for some variants of revision + <= r0p4. This workaround can lead the linker to emit ``*.stub`` sections + which are 4kB aligned. + +- ``ERRATA_A53_855873``: This applies errata 855873 workaround to Cortex-A53 + CPUs. Though the erratum is present in every revision of the CPU, + this workaround is only applied to CPUs from r0p3 onwards, which feature + a chicken bit in CPUACTLR_EL1 to enable a hardware workaround. + Earlier revisions of the CPU have other errata which require the same + workaround in software, so they should be covered anyway. + +For Cortex-A55, the following errata build flags are defined : + +- ``ERRATA_A55_768277``: This applies errata 768277 workaround to Cortex-A55 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A55_778703``: This applies errata 778703 workaround to Cortex-A55 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A55_798797``: This applies errata 798797 workaround to Cortex-A55 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A55_846532``: This applies errata 846532 workaround to Cortex-A55 + CPU. This needs to be enabled only for revision <= r0p1 of the CPU. + +- ``ERRATA_A55_903758``: This applies errata 903758 workaround to Cortex-A55 + CPU. This needs to be enabled only for revision <= r0p1 of the CPU. + +For Cortex-A57, the following errata build flags are defined : + +- ``ERRATA_A57_806969``: This applies errata 806969 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A57_813419``: This applies errata 813419 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A57_813420``: This applies errata 813420 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A57_814670``: This applies errata 814670 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A57_817169``: This applies errata 817169 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r0p1 of the CPU. + +- ``ERRATA_A57_826974``: This applies errata 826974 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p1 of the CPU. + +- ``ERRATA_A57_826977``: This applies errata 826977 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p1 of the CPU. + +- ``ERRATA_A57_828024``: This applies errata 828024 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p1 of the CPU. + +- ``ERRATA_A57_829520``: This applies errata 829520 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p2 of the CPU. + +- ``ERRATA_A57_833471``: This applies errata 833471 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p2 of the CPU. + +- ``ERRATA_A57_859972``: This applies errata 859972 workaround to Cortex-A57 + CPU. This needs to be enabled only for revision <= r1p3 of the CPU. + + +For Cortex-A72, the following errata build flags are defined : + +- ``ERRATA_A72_859971``: This applies errata 859971 workaround to Cortex-A72 + CPU. This needs to be enabled only for revision <= r0p3 of the CPU. + +For Cortex-A73, the following errata build flags are defined : + +- ``ERRATA_A73_852427``: This applies errata 852427 workaround to Cortex-A73 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A73_855423``: This applies errata 855423 workaround to Cortex-A73 + CPU. This needs to be enabled only for revision <= r0p1 of the CPU. + +For Cortex-A75, the following errata build flags are defined : + +- ``ERRATA_A75_764081``: This applies errata 764081 workaround to Cortex-A75 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +- ``ERRATA_A75_790748``: This applies errata 790748 workaround to Cortex-A75 + CPU. This needs to be enabled only for revision r0p0 of the CPU. + +For Cortex-A76, the following errata build flags are defined : + +- ``ERRATA_A76_1073348``: This applies errata 1073348 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r1p0 of the CPU. + +- ``ERRATA_A76_1130799``: This applies errata 1130799 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r2p0 of the CPU. + +- ``ERRATA_A76_1220197``: This applies errata 1220197 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r2p0 of the CPU. + +- ``ERRATA_A76_1257314``: This applies errata 1257314 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r3p0 of the CPU. + +- ``ERRATA_A76_1262606``: This applies errata 1262606 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r3p0 of the CPU. + +- ``ERRATA_A76_1262888``: This applies errata 1262888 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r3p0 of the CPU. + +- ``ERRATA_A76_1275112``: This applies errata 1275112 workaround to Cortex-A76 + CPU. This needs to be enabled only for revision <= r3p0 of the CPU. + +DSU Errata Workarounds +---------------------- + +Similar to CPU errata, TF-A also implements workarounds for DSU (DynamIQ +Shared Unit) errata. The DSU errata details can be found in the respective Arm +documentation: + +- `Arm DSU Software Developers Errata Notice`_. + +Each erratum is identified by an ``ID``, as defined in the DSU errata notice +document. Thus, the build flags which enable/disable the errata workarounds +have the format ``ERRATA_DSU_<ID>``. The implementation and application logic +of DSU errata workarounds are similar to `CPU errata workarounds`_. + +For DSU errata, the following build flags are defined: + +- ``ERRATA_DSU_798953``: This applies errata 798953 workaround for the + affected DSU configurations. This errata applies only for those DSUs that + revision is r0p0 (on r0p1 it is fixed). However, please note that this + workaround results in increased DSU power consumption on idle. + +- ``ERRATA_DSU_936184``: This applies errata 936184 workaround for the + affected DSU configurations. This errata applies only for those DSUs that + contain the ACP interface **and** the DSU revision is older than r2p0 (on + r2p0 it is fixed). However, please note that this workaround results in + increased DSU power consumption on idle. + +CPU Specific optimizations +-------------------------- + +This section describes some of the optimizations allowed by the CPU micro +architecture that can be enabled by the platform as desired. + +- ``SKIP_A57_L1_FLUSH_PWR_DWN``: This flag enables an optimization in the + Cortex-A57 cluster power down sequence by not flushing the Level 1 data + cache. The L1 data cache and the L2 unified cache are inclusive. A flush + of the L2 by set/way flushes any dirty lines from the L1 as well. This + is a known safe deviation from the Cortex-A57 TRM defined power down + sequence. Each Cortex-A57 based platform must make its own decision on + whether to use the optimization. + +- ``A53_DISABLE_NON_TEMPORAL_HINT``: This flag disables the cache non-temporal + hint. The LDNP/STNP instructions as implemented on Cortex-A53 do not behave + in a way most programmers expect, and will most probably result in a + significant speed degradation to any code that employs them. The Armv8-A + architecture (see Arm DDI 0487A.h, section D3.4.3) allows cores to ignore + the non-temporal hint and treat LDNP/STNP as LDP/STP instead. Enabling this + flag enforces this behaviour. This needs to be enabled only for revisions + <= r0p3 of the CPU and is enabled by default. + +- ``A57_DISABLE_NON_TEMPORAL_HINT``: This flag has the same behaviour as + ``A53_DISABLE_NON_TEMPORAL_HINT`` but for Cortex-A57. This needs to be + enabled only for revisions <= r1p2 of the CPU and is enabled by default, + as recommended in section "4.7 Non-Temporal Loads/Stores" of the + `Cortex-A57 Software Optimization Guide`_. + +-------------- + +*Copyright (c) 2014-2019, Arm Limited and Contributors. All rights reserved.* + +.. _CVE-2017-5715: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715 +.. _CVE-2018-3639: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-3639 +.. _Cortex-A53 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm048406/index.html +.. _Cortex-A57 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm049219/index.html +.. _Cortex-A72 MPCore Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm012079/index.html +.. _Firmware Design guide: firmware-design.rst +.. _Cortex-A57 Software Optimization Guide: http://infocenter.arm.com/help/topic/com.arm.doc.uan0015b/Cortex_A57_Software_Optimization_Guide_external.pdf +.. _Arm DSU Software Developers Errata Notice: http://infocenter.arm.com/help/topic/com.arm.doc.epm138168/index.html |