path: root/Documentation/arm64
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authorMark Brown <broonie@kernel.org>2021-04-12 16:19:53 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2021-04-30 18:53:42 +0100
commitee61f36d3e46bdb1c8910d1bd5c0863130c7b951 (patch)
tree57aebfb36ec13b722203080f440789e6ff97359a /Documentation/arm64
parentarm64: cpufeatures: use min and max (diff)
arm64: Relax booting requirements for configuration of traps
Currently we require that a number of system registers be configured to disable traps when starting the kernel. Add an explicit note that the requirement is that the system behave as if the traps are disabled so transparent handling of the traps is fine, this should be implicit for people familiar with working with standards documents but it doesn't hurt to be explicit. Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20210412151955.16078-2-broonie@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'Documentation/arm64')
1 files changed, 4 insertions, 1 deletions
diff --git a/Documentation/arm64/booting.rst b/Documentation/arm64/booting.rst
index 4fcc00add117..b21049ab6c69 100644
--- a/Documentation/arm64/booting.rst
+++ b/Documentation/arm64/booting.rst
@@ -279,7 +279,10 @@ Before jumping into the kernel, the following conditions must be met:
The requirements described above for CPU mode, caches, MMUs, architected
timers, coherency and system registers apply to all CPUs. All CPUs must
-enter the kernel in the same exception level.
+enter the kernel in the same exception level. Where the values documented
+disable traps it is permissible for these traps to be enabled so long as
+those traps are handled transparently by higher exception levels as though
+the values documented were set.
The boot loader is expected to enter the kernel on each CPU in the
following manner: