• Paul Mackerras's avatar
    powerpc: Provide a way for KVM to indicate that NV GPR values are lost · 2fde6d20
    Paul Mackerras authored
    This fixes a problem where a CPU thread coming out of nap mode can
    think it has valid values in the nonvolatile GPRs (r14 - r31) as saved
    away in power7_idle, but in fact the values have been trashed because
    the thread was used for KVM in the mean time.  The result is that the
    thread crashes because code that called power7_idle (e.g.,
    pnv_smp_cpu_kill_self()) goes to use values in registers that have
    been trashed.
    
    The bit field in SRR1 that tells whether state was lost only reflects
    the most recent nap, which may not have been the nap instruction in
    power7_idle.  So we need an extra PACA field to indicate that state
    has been lost even if SRR1 indicates that the most recent nap didn't
    lose state.  We clear this field when saving the state in power7_idle,
    we set it to a non-zero value when we use the thread for KVM, and we
    test it in power7_wakeup_noloss.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    2fde6d20
idle_power7.S 2.13 KB