[PATCH v4 17/21] KVM: arm64: Document HVC_VHE_RESTART stub hypercall

From: Marc Zyngier
Date: Mon Jan 18 2021 - 16:39:32 EST

For completeness, let's document the HVC_VHE_RESTART stub.

Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Documentation/virt/kvm/arm/hyp-abi.rst | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/Documentation/virt/kvm/arm/hyp-abi.rst b/Documentation/virt/kvm/arm/hyp-abi.rst
index 83cadd8186fa..1ba628baf11b 100644
--- a/Documentation/virt/kvm/arm/hyp-abi.rst
+++ b/Documentation/virt/kvm/arm/hyp-abi.rst
@@ -58,6 +58,15 @@ these functions (see arch/arm{,64}/include/asm/virt.h):
into place (arm64 only), and jump to the restart address while at HYP/EL2.
This hypercall is not expected to return to its caller.

+* ::
+ x0 = HVC_VHE_RESTART (arm64 only)
+ Attempt to upgrade the kernel's exception level from EL1 to EL2 by enabling
+ the VHE mode. This is conditioned by the CPU supporting VHE, the EL2 MMU
+ being off, and VHE not being disabled by any other mean (comment line option,
+ for example).
Any other value of r0/x0 triggers a hypervisor-specific handling,
which is not documented here.