On Tue, 16 May 2017 14:19:44 +0530 "Gautham R. Shenoy" <e...@linux.vnet.ibm.com> wrote:
> From: "Gautham R. Shenoy" <e...@linux.vnet.ibm.com> > > On POWER8, in case of > - nap: both timebase and hypervisor state is retained. > - fast-sleep: timebase is lost. But the hypervisor state is retained. > - winkle: timebase and hypervisor state is lost. > > Hence, the current code for handling exit from a idle state assumes > that if the timebase value is retained, then so is the hypervisor > state. Thus, the current code doesn't restore per-core hypervisor > state in such cases. > > But that is no longer the case on POWER9 where we do have stop states > in which timebase value is retained, but the hypervisor state is > lost. So we have to ensure that the per-core hypervisor state gets > restored in such cases. > > Fix this by ensuring that even in the case when timebase is retained, > we explicitly check if we are waking up from a deep stop that loses > per-core hypervisor state (indicated by cr4 being eq or gt), and if > this is the case, we restore the per-core hypervisor state. > > Signed-off-by: Gautham R. Shenoy <e...@linux.vnet.ibm.com> > --- > arch/powerpc/kernel/idle_book3s.S | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kernel/idle_book3s.S > b/arch/powerpc/kernel/idle_book3s.S > index 4898d67..afd029f 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -731,13 +731,14 @@ timebase_resync: > * Use cr3 which indicates that we are waking up with atleast partial > * hypervisor state loss to determine if TIMEBASE RESYNC is needed. > */ > - ble cr3,clear_lock > + ble cr3,.Ltb_resynced > /* Time base re-sync */ > bl opal_resync_timebase; > /* > - * If waking up from sleep, per core state is not lost, skip to > - * clear_lock. > + * If waking up from sleep (POWER8), per core state > + * is not lost, skip to clear_lock. > */ > +.Ltb_resynced: > blt cr4,clear_lock > > /* It's more that timebase was not lost, rather than resynced. Can we just do a 'bgtl cr3,opal_resync_timebase'? I guess cr4 branch will never be true on POWER9... I think pnv_wakeup_tb_loss is going to end up clearer being split into two between isa 207 and 300. But that can wait until after POWER9 is working properly. Reviewed-by: Nicholas Piggin <npig...@gmail.com>
