path: root/Documentation/arm
diff options
authorDave Martin <dave.martin@linaro.org>2012-02-10 18:07:07 -0800
committerMarc Zyngier <marc.zyngier@arm.com>2012-09-19 08:32:51 +0100
commit6a6d55c38c8b4ee77b50a33f03ea09e75b18bf82 (patch)
tree5aa95a02f40aabc081fef2d454baaa3009352163 /Documentation/arm
parent424e5994e63326a42012f003f1174f3c363c7b62 (diff)
ARM: virt: Update documentation for hyp mode entry support
Document the possibility of the kernel being entered in HYP mode. Signed-off-by: Dave Martin <dave.martin@linaro.org> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'Documentation/arm')
1 files changed, 21 insertions, 1 deletions
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting
index a341d87d276..0c1f475fdf3 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.