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-rw-r--r--Documentation/arm/Booting22
1 files changed, 21 insertions, 1 deletions
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting
index a341d87..0c1f475 100644
--- a/Documentation/arm/Booting
+++ b/Documentation/arm/Booting
@@ -154,13 +154,33 @@ In either case, the following conditions must be met:
- CPU mode
All forms of interrupts must be disabled (IRQs and FIQs)
- The CPU must be in SVC mode. (A special exception exists for Angel)
+
+ For CPUs which do not include the ARM virtualization extensions, the
+ CPU must be in SVC mode. (A special exception exists for Angel)
+
+ CPUs which include support for the virtualization extensions can be
+ entered in HYP mode in order to enable the kernel to make full use of
+ these extensions. This is the recommended boot method for such CPUs,
+ unless the virtualisations are already in use by a pre-installed
+ hypervisor.
+
+ If the kernel is not entered in HYP mode for any reason, it must be
+ entered in SVC mode.
- Caches, MMUs
The MMU must be off.
Instruction cache may be on or off.
Data cache must be off.
+ If the kernel is entered in HYP mode, the above requirements apply to
+ the HYP mode configuration in addition to the ordinary PL1 (privileged
+ kernel modes) configuration. In addition, all traps into the
+ hypervisor must be disabled, and PL1 access must be granted for all
+ peripherals and CPU resources for which this is architecturally
+ possible. Except for entering in HYP mode, the system configuration
+ should be such that a kernel which does not include support for the
+ virtualization extensions can boot correctly without extra help.
+
- The boot loader is expected to call the kernel image by jumping
directly to the first instruction of the kernel image.