Both arm and arm64 kernel entry point have the following prerequisite:
MMU = off, D-cache = off, I-cache = dont care.
HVC_SOFT_RESTART call should meet this prerequisite before jumping to the
new kernel.
Furthermore, on arm64, el2_setup doesn't set I+C bits and keeps EL2 MMU
off, and KVM resets them when its unload. These are achieved by
HVC_RESET_VECTORS call.
Improve the document.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Julien Thierry <julien.thierry.kdev@xxxxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
To: kvmarm@xxxxxxxxxxxxxxxxxxxxx
---
Documentation/virt/kvm/arm/hyp-abi.rst | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/Documentation/virt/kvm/arm/hyp-abi.rst b/Documentation/virt/kvm/arm/hyp-abi.rst
index d9eba93..a95bc30 100644
--- a/Documentation/virt/kvm/arm/hyp-abi.rst
+++ b/Documentation/virt/kvm/arm/hyp-abi.rst
@@ -40,9 +40,9 @@ these functions (see arch/arm{,64}/include/asm/virt.h):
* ::
- r0/x0 = HVC_RESET_VECTORS
+ x0 = HVC_RESET_VECTORS (arm64 only)
- Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials
+ Disable HYP/EL2 MMU and D-cache, and reset HVBAR/VBAR_EL2 to the initials
stubs' exception vector value. This effectively disables an existing
hypervisor.
@@ -54,7 +54,7 @@ these functions (see arch/arm{,64}/include/asm/virt.h):
x3 = x1's value when entering the next payload (arm64)
x4 = x2's value when entering the next payload (arm64)
- Mask all exceptions, disable the MMU, move the arguments into place
+ Mask all exceptions, disable the MMU and D-cache, move the arguments into place
(arm64 only), and jump to the restart address while at HYP/EL2. This
hypercall is not expected to return to its caller.
--
2.7.5
