• Nicholas Piggin's avatar
    powerpc/64s: Avoid cpabort in context switch when possible · 07d2a628
    Nicholas Piggin authored
    The ISA v3.0B copy-paste facility only requires cpabort when switching
    to a process that has foreign real addresses mapped (direct access to
    accelerators), to clear a potential copy buffer filled by a previous
    thread. There is no accelerator driver implemented yet, so cpabort can
    be removed. It can be be re-added when a driver is implemented.
    
    POWER9 DD1 requires the copy buffer to always be cleared on context
    switch, but if accelerators are not in use, then an unpaired copy from
    a dummy region is sufficient to clear data out of the copy buffer.
    
    This increases context switch performance by about 5% on POWER9.
    Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    07d2a628
entry_64.S 28.8 KB