On Fri, 7 Jul 2017 23:07:10 +0530 Gautham R Shenoy <e...@linux.vnet.ibm.com> wrote:
> On Fri, Jul 07, 2017 at 01:29:16AM +1000, Nicholas Piggin wrote: > > On Wed, 5 Jul 2017 22:08:16 +0530 > > "Gautham R. Shenoy" <e...@linux.vnet.ibm.com> wrote: > > > > > From: "Gautham R. Shenoy" <e...@linux.vnet.ibm.com> > > > > > > Currently, we use the opal call opal_slw_set_reg() to inform the that > > > the Sleep-Winkle Engine (SLW) to restore the contents of some of the > > > Hypervisor state on wakeup from deep idle states that lose full > > > hypervisor context (characterized by the flag > > > OPAL_PM_LOSE_FULL_CONTEXT). > > > > > > However, the current code has a bug in that if opal_slw_set_reg() > > > fails, we don't disable the use of these deep states (winkle on > > > POWER8, stop4 onwards on POWER9). > > > > > > This patch fixes this bug by ensuring that if the the sleep winkle > > > engine is unable to restore the hypervisor states in > > > pnv_save_sprs_for_deep_states(), then we mark as invalid the states > > > which lose full context. > > > > > > As a side-effect, since supported_cpuidle_states in > > > pnv_probe_idle_states() consists of flags of only the valid states, > > > this patch will ensure that no other subsystem in the kernel can use > > > the states which lose full context on stop-api failures. > > > > Looks good. Is there something minimal we can do for stable here? > > > > Aside question, do we need to restore LPCR at all with the SLW engine? > > It gets set up again when by the idle wakeup code. > > > > > > And does POWER9 really need MSR and PSSCR restored by SLW? (going a bit > > off topic here, I'm just curious) > > MSR is needed to be restored so that we wakeup with the right > endianness and with the IR,DR disabled. And POWER8 does not require this? > PSSCR is set to a value so that in case of a special wakeup for a > deep-stop, the SLW can program the core to go back to the stop level > provided by the PSSCR value via the stop-api. It always restores to deepest stop? Is there any way to restore to the achieved stop level? Maybe there is no usefulness for that. Thanks, Nick
