On Fri, 01 Sep 2017 19:39:41 +1000
Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
> Nicholas Piggin <npiggin@xxxxxxxxx> writes:
>
> > On Wed, 30 Aug 2017 21:25:59 +1000
> > Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
> >
> >> Nicholas Piggin <npiggin@xxxxxxxxx> writes:
> >>
> >> > When stop is executed with EC=ESL=0, it appears to execute like a
> >> > normal instruction (resuming from NIP when woken by interrupt).
> >> > So all the save/restore handling can be avoided completely. In
> >> > particular NV GPRs do not have to be saved, and MSR does not have
> >> > to be switched back to kernel MSR.
> >> >
> >> > So move the test for "lite" sleep states out to power9_idle_stop.
> >> >
> >> > Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
> >> > Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> >> > ---
> >> > arch/powerpc/kernel/idle_book3s.S | 35 ++++++++++++++++++++++++-----------
> >> > 1 file changed, 24 insertions(+), 11 deletions(-)
> >>
> >> This is blowing up for me on mambo:
> >
> > Oh this is a known bug in mambo that does not match the hardware.
> >
> > You need >= Mambo.7.8.21, or this firmware patch to work around
> > the issue for old mambos.
>
> As discussed elsewhere this still breaks on new mambo with more than one
> CPU. So I've dropped it for now.
This now seems to be properly fixed in mambo with commit 11783550ee11.
Skiboot also has a patch merged which disables the problematic state on
mambo so older versions won't crash.
d2a24406a49 ("idle: disable stop*_lite POWER9 idle states for Mambo platform")
So this could be re-applied now.
Thanks,
Nick
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