On Thu, 13 Apr 2017 17:24:34 +0530 Gautham R Shenoy <e...@linux.vnet.ibm.com> wrote:
> On Thu, Apr 13, 2017 at 05:18:17PM +1000, Nicholas Piggin wrote: > > On Thu, 13 Apr 2017 16:27:34 +1000 > > Michael Neuling <mi...@neuling.org> wrote: > > > > > On Thu, 2017-04-13 at 14:12 +1000, Benjamin Herrenschmidt wrote: > > > > On Thu, 2017-04-13 at 09:28 +0530, Aneesh Kumar K.V wrote: > > > > > > #endif > > > > > > mtctr r12 > > > > > > bctrl > > > > > > +/* > > > > > > + * cur_cpu_spec->cpu_restore would restore LPCR to a > > > > > > + * sane value that is set at early boot time, > > > > > > + * thereby clearing LPCR_UPRT. > > > > > > + * LPCR_UPRT is required if we are running in Radix mode. > > > > > > + * Set it here if that be the case. > > > > > > + */ > > > > > > +BEGIN_MMU_FTR_SECTION > > > > > > + mfspr r3, SPRN_LPCR > > > > > > + LOAD_REG_IMMEDIATE(r4, LPCR_UPRT) > > > > > > + or r3, r3, r4 > > > > > > + mtspr SPRN_LPCR, r3 > > > > > > +END_MMU_FTR_SECTION_IFSET(MMU_FTR_TYPE_RADIX) > > > > > > > > We are probably better off saving the value somewhere during boot > > > > and just "blasting" it whole back. > > > > > > We seem to touch LPCR in a bunch of places these days. Not sure when > > > "sometimes > > > during boot" should actually be. > > > > In the short term, what if we just save LPCR and restore it after calling > > cpu_restore? As you say there are a lot of things that touch LPCR we're > > not catching here. > > In that case can we skip calling cpu_restore in the idle_exit path > altogether and simply restore LPCR to the value that the thread had > before executing stop ? Good question. For a minimal fix I would keep calling cpu_restore. I'd like to get rid of it if we can though, but that might take a bit more work.