The new document will help to keep track of all the erratum that Xen is able to handle.
The text is based on the Linux doc in Documents/arm64/silicon-errata.txt. Also list the current errata that Xen is aware of. Signed-off-by: Julien Grall <julien.gr...@arm.com> --- docs/misc/arm/silicon-errata.txt | 45 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 docs/misc/arm/silicon-errata.txt diff --git a/docs/misc/arm/silicon-errata.txt b/docs/misc/arm/silicon-errata.txt new file mode 100644 index 0000000..3f0d32b --- /dev/null +++ b/docs/misc/arm/silicon-errata.txt @@ -0,0 +1,45 @@ + Silicon Errata and Software Workarounds + ======================================= + +It is an unfortunate fact of life that hardware is often produced with +so-called "errata", which can cause it to deviate from the architecture +under specific circumstances. For hardware produced by ARM, these +errata are broadly classified into the following categories: + + Category A: A critical error without a viable workaround. + Category B: A significant or critical error with an acceptable + workaround. + Category C: A minor error that is not expected to occur under normal + operation. + +For more information, consult one of the "Software Developers Errata +Notice" documents available on infocenter.arm.com (registration +required). + +As far as Xen is concerned, Category B errata may require some special +treatment in the hypervisor. For example, avoiding a particular sequence +of code, or configuring the processor in a particular way. A less common +situation may require similar actions in order to declassify a Category A +erratum into a Category C erratum. These are collectively known as +"software workarounds" and are only required in the minority of cases +(e.g. those cases that both require a non-secure workaround *and* can +be triggered by Linux). + +For software workarounds that may adversely impact systems unaffected by +the erratum in question, a Kconfig entry is added under "ARM errata +workarounds via the alternatives framework". These are enabled by default +and patched in at runtime when an affected CPU is detected. For +less-intrusive workarounds, a Kconfig option is not available and the code +is structured (preferably with a comment) in such a way that the erratum +will not be hit. + +This approach can make it slightly onerous to determine exactly which +errata are worked around in an arbitrary hypervisor source tree, so this +file acts as a registry of software workarounds in the Xen hypervisor and +will be updated when new workarounds are committed and backported to +stable hypervisors. + +| Implementor | Component | Erratum ID | Kconfig | ++----------------+-----------------+-----------------+-------------------------+ +| ARM | Cortex-A15 | #766422 | N/A | +| ARM | Cortex-A57 | #852523 | N/A | -- 1.9.1 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
