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+ 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 |
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.grall@arm.com> --- docs/misc/arm/silicon-errata.txt | 45 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 docs/misc/arm/silicon-errata.txt