• James Morse's avatar
    arm64: cpufeature: Schedule enable() calls instead of calling them via IPI · 2a6dcb2b
    James Morse authored
    
    
    The enable() call for a cpufeature/errata is called using on_each_cpu().
    This issues a cross-call IPI to get the work done. Implicitly, this
    stashes the running PSTATE in SPSR when the CPU receives the IPI, and
    restores it when we return. This means an enable() call can never modify
    PSTATE.
    
    To allow PAN to do this, change the on_each_cpu() call to use
    stop_machine(). This schedules the work on each CPU which allows
    us to modify PSTATE.
    
    This involves changing the protype of all the enable() functions.
    
    enable_cpu_capabilities() is called during boot and enables the feature
    on all online CPUs. This path now uses stop_machine(). CPU features for
    hotplug'd CPUs are enabled by verify_local_cpu_features() which only
    acts on the local CPU, and can already modify the running PSTATE as it
    is called from secondary_start_kernel().
    Reported-by: default avatarTony Thompson <anthony.thompson@arm.com>
    Reported-by: default avatarVladimir Murzin <vladimir.murzin@arm.com>
    Signed-off-by: default avatarJames Morse <james.morse@arm.com>
    Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    2a6dcb2b
traps.c 17 KB