Firmware interface for AArch64

The firmware interface provided by QNX Hypervisor VMs on AArch64 (ARMv8) platforms adheres to the Secure Monitor Call Calling Convention (SMCCC) which governs the use of the SMC and HVC (HyperVisor Call) instructions. This interface includes the ARM Architecture Service, ParaVirtualized Timer (PV TIMER), and Power State Coordination Interface (PSCI) services.

The conventions followed by this interface are fully described in the SMC Calling Conventions document that is available at: https://developer.arm.com/documentation/den0028/c.

The conduit (mechanism) that QNX Hypervisor supports for calling firmware functions is the HVC machine instruction, which accepts a function ID to indicate the call being made. The HVC instruction generates a synchronous exception that the hypervisor handles, running at exception level 2 (EL2). Arguments and return values are passed in registers.

The SMCCC specification defines function ID ranges for the various HVC-accessed services while other ARM specifications further define individual services and functions. The table that follows describes the firmware services supported by qvm (i.e., the VMs), including the total range of function IDs reserved for each service.

The sections that follow list the individual functions of each service and whether they are emulated by qvm, forwarded to the host hardware, or not supported. The unsupported functions are included to clarify which firmware operations guest OSs can or cannot perform via the VMs, and also to give insight into the overall design of these services.