• Jeenu Viswambharan's avatar
    Introduce ARM SiP service to switch execution state · b10d4499
    Jeenu Viswambharan authored
    
    
    In AArch64, privileged exception levels control the execution state
    (a.k.a. register width) of the immediate lower Exception Level; i.e.
    whether the lower exception level executes in AArch64 or AArch32 state.
    For an exception level to have its execution state changed at run time,
    it must request the change by raising a synchronous exception to the
    higher exception level.
    
    This patch implements and adds such a provision to the ARM SiP service,
    by which an immediate lower exception level can request to switch its
    execution state. The execution state is switched if the request is:
    
      - raised from non-secure world;
    
      - raised on the primary CPU, before any secondaries are brought online
        with CPU_ON PSCI call;
    
      - raised from an exception level immediately below EL3: EL2, if
        implemented; otherwise NS EL1.
    
    If successful, the SMC doesn't return to the caller, but to the entry
    point supplied with the call. Otherwise, the caller will observe the SMC
    returning with STATE_SW_E_DENIED code. If ARM Trusted Firmware is built
    for AArch32, the feature is not supported, and the call will always
    fail.
    
    For the ARM SiP service:
    
      - Add SMC function IDs for both AArch32 and AArch64;
      - Increment the SiP service minor version to 2;
      - Adjust the number of supported SiP service calls.
    
    Add documentation for ARM SiP service.
    
    Fixes ARM-software/tf-issues#436
    
    Change-Id: I4347f2d6232e69fbfbe333b340fcd0caed0a4cea
    Signed-off-by: default avatarJeenu Viswambharan <jeenu.viswambharan@arm.com>
    b10d4499
context_mgmt.h 4.2 KB