[PATCH v4 27/30] KVM: arm64: Document the KVM/arm64-specific calls in hypercalls.rst

[Fuad Tabba <tabba@google.com>]

From: Will Deacon <will@kernel.org>

KVM/arm64 makes use of the SMCCC "Vendor Specific Hypervisor Service
Call Range" to expose KVM-specific hypercalls to guests in a
discoverable and extensible fashion.

Document the existence of this interface and the discovery hypercall.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
---
 Documentation/virt/kvm/arm/hypercalls.rst | 46 +++++++++++++++++++++++
 Documentation/virt/kvm/arm/index.rst      |  1 +
 2 files changed, 47 insertions(+)
 create mode 100644 Documentation/virt/kvm/arm/hypercalls.rst

diff --git a/Documentation/virt/kvm/arm/hypercalls.rst b/Documentation/virt/kvm/arm/hypercalls.rst
new file mode 100644
index 000000000000..17be111f493f
--- /dev/null
+++ b/Documentation/virt/kvm/arm/hypercalls.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================================
+KVM/arm64-specific hypercalls exposed to guests
+===============================================
+
+This file documents the KVM/arm64-specific hypercalls which may be
+exposed by KVM/arm64 to guest operating systems. These hypercalls are
+issued using the HVC instruction according to version 1.1 of the Arm SMC
+Calling Convention (DEN0028/C):
+
+https://developer.arm.com/docs/den0028/c
+
+All KVM/arm64-specific hypercalls are allocated within the "Vendor
+Specific Hypervisor Service Call" range with a UID of
+``28b46fb6-2ec5-11e9-a9ca-4b564d003a74``. This UID should be queried by the
+guest using the standard "Call UID" function for the service range in
+order to determine that the KVM/arm64-specific hypercalls are available.
+
+``ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID``
+---------------------------------------------
+
+Provides a discovery mechanism for other KVM/arm64 hypercalls.
+
++---------------------+-------------------------------------------------------------+
+| Presence:           | Mandatory for the KVM/arm64 UID                             |
++---------------------+-------------------------------------------------------------+
+| Calling convention: | HVC32                                                       |
++---------------------+----------+--------------------------------------------------+
+| Function ID:        | (uint32) | 0x86000000                                       |
++---------------------+----------+--------------------------------------------------+
+| Arguments:          | None                                                        |
++---------------------+----------+----+---------------------------------------------+
+| Return Values:      | (uint32) | R0 | Bitmap of available function numbers 0-31   |
+|                     +----------+----+---------------------------------------------+
+|                     | (uint32) | R1 | Bitmap of available function numbers 32-63  |
+|                     +----------+----+---------------------------------------------+
+|                     | (uint32) | R2 | Bitmap of available function numbers 64-95  |
+|                     +----------+----+---------------------------------------------+
+|                     | (uint32) | R3 | Bitmap of available function numbers 96-127 |
++---------------------+----------+----+---------------------------------------------+
+
+``ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID``
+----------------------------------------
+
+See ptp_kvm.rst
diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst
index d28d65122290..ec09881de4cf 100644
--- a/Documentation/virt/kvm/arm/index.rst
+++ b/Documentation/virt/kvm/arm/index.rst
@@ -9,6 +9,7 @@ ARM
 
    fw-pseudo-registers
    hyp-abi
+   hypercalls
    pvtime
    ptp_kvm
    vcpu-features
-- 
2.44.0.769.g3c40516874-goog