• David S. Miller's avatar
    [SPARC64]: Initial LDOM cpu hotplug support. · 4f0234f4
    David S. Miller authored
    Only adding cpus is supports at the moment, removal
    will come next.
    
    When new cpus are configured, the machine description is
    updated.  When we get the configure request we pass in a
    cpu mask of to-be-added cpus to the mdesc CPU node parser
    so it only fetches information for those cpus.  That code
    also proceeds to update the SMT/multi-core scheduling bitmaps.
    
    cpu_up() does all the work and we return the status back
    over the DS channel.
    
    CPUs via dr-cpu need to be booted straight out of the
    hypervisor, and this requires:
    
    1) A new trampoline mechanism.  CPUs are booted straight
       out of the hypervisor with MMU disabled and running in
       physical addresses with no mappings installed in the TLB.
    
       The new hvtramp.S code sets up the critical cpu state,
       installs the locked TLB mappings for the kernel, and
       turns the MMU on.  It then proceeds to follow the logic
       of the existing trampoline.S SMP cpu bringup code.
    
    2) All calls into OBP have to be disallowed when domaining
       is enabled.  Since cpus boot straight into the kernel from
       the hypervisor, OBP has no state about that cpu and therefore
       cannot handle being invoked on that cpu.
    
       Luckily it's only a handful of interfaces which can be called
       after the OBP device tree is obtained.  For example, rebooting,
       halting, powering-off, and setting options node variables.
    
    CPU removal support will require some infrastructure changes
    here.  Namely we'll have to process the requests via a true
    kernel thread instead of in a workqueue.  workqueues run on
    a per-cpu thread, but when unconfiguring we might need to
    force the thread to execute on another cpu if the current cpu
    is the one being removed.  Removal of a cpu also causes the kernel
    to destroy that cpu's workqueue running thread.
    
    Another issue on removal is that we may have interrupts still
    pointing to the cpu-to-be-removed.  So new code will be needed
    to walk the active INO list and retarget those cpus as-needed.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    4f0234f4
hvtramp.S 2.64 KB