On Mon, 2010-09-27 at 11:04 -0400, Josh Boyer wrote: > On Fri, Sep 24, 2010 at 01:01:36PM -0500, Dave Kleikamp wrote: > >When the DSTI (Disable Shadow TLB Invalidate) bit is set in the CCR2 > >register, the isync command does not flush the shadow TLB (iTLB & dTLB). > > > >However, since the shadow TLB does not contain context information, we > >want the shadow TLB flushed in situations where we are switching context. > >In those situations, we explicitly clear the DSTI bit before performing > >isync, and set it again afterward. We also need to do the same when we > >perform isync after explicitly flushing the TLB. > > > >Th setting of the DSTI bit is dependent on > >CONFIG_PPC_47x_DISABLE_SHADOW_TLB_INVALIDATE. When we are confident that > >the feature works as expected, the option can probably be removed. > > You're defaulting it to 'y' in the Kconfig. Technically someone could > turn it off I guess, but practice mostly shows that nobody mucks with > the defaults. Do you want it to default 'n' for now if you aren't > confident in it just quite yet?
I think I made it a config option at Ben's request when I first started this work last year, before being sidetracked by other priorities. I could either remove the option, or default it to 'n'. It might be best to just hard-code the behavior to make sure it's exercised, since there's no 47x hardware in production yet, but we can give Ben a chance to weigh in with his opinion. > (Linus also has some kind of gripe with new options being default 'y', > but I don't recall all the details and I doubt he'd care about something > in low-level PPC code.) > > josh -- Dave Kleikamp IBM Linux Technology Center _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
