On Wed, 2015-10-07 at 20:15 -0400, Josh Boyer wrote: > On Wed, Oct 7, 2015 at 8:10 PM, Michael Ellerman <m...@ellerman.id.au> wrote: > > On Wed, 2015-10-07 at 10:31 -0400, Josh Boyer wrote: > >> On Wed, Oct 7, 2015 at 5:13 AM, Michael Ellerman <m...@ellerman.id.au> > >> wrote: > >> > On Wed, 2015-10-07 at 02:19 -0500, Segher Boessenkool wrote: > >> >> On Wed, Oct 07, 2015 at 05:00:49PM +1100, Michael Ellerman wrote: > >> >> > > It's also worth noting that the __flush_power7 uses tlbiel instead > >> >> > > of tlbie. > >> >> > > >> >> > Yeah that's a good point. It's not clear if the swsusp code wants to > >> >> > a local or > >> >> > a global invalidate. > >> >> > >> >> If I read the code right, this is called on the boot CPU when all the > >> >> non-boot CPUs are still (potentially) down, so if you would do a global > >> >> invalidate the non-boot CPUs might not even notice, so those need to do > >> >> a (local) invalidate after being brought up anyway? Or they probably > >> >> need it before being brought down at all? You figure it out, it makes > >> >> my brain hurt :-) > >> > > >> > A good rule would be that every cpu does a local invalidate before > >> > turning on > >> > the MMU. That would work for this case and also for kexec, kdump, junk > >> > left by > >> > firmare etc. But I don't think we do that consistently in a way that > >> > works for > >> > this code at the moment. > >> > > >> >> > As an alternative, can you try adding a .machine push / .machine > >> >> > "power4" / > >> >> > .machine pop, around the tlbie. That should tell the assembler to > >> >> > drop back to > >> >> > power4 mode for that instruction, which should then do the right > >> >> > thing. There > >> >> > are some examples in that file. > >> >> > >> >> That will get the assembler to not complain, but it will assemble the > >> >> wrong > >> >> instruction: the power7 instruction has the same opcode (but different > >> >> semantics). So if you assemble a "tlbie r4" in power4 mode, a newer CPU > >> >> will see it as a "tlbie r4,r0" and do the wrong thing. > >> > > >> > Yeah, it would basically maintain the existing behaviour which is wrong > >> > but a > >> > known quantity. I suspect no one has ever run this on Power7 or in fact > >> > anything other than G5 or Book3E. > >> > >> Likely not, but leaving it broken just because it is known behavior > >> seems pretty weird to me. > > > > In a universe where I have infinite time to fix random things we would > > obviously do a proper fix :) > > > >> I think Fedora will look at simply disabling hibernation on ppc64 so the > >> file > >> isn't built at all. Seems to be a safer option. > > > > It's safer for sure. Though you might have some G5 users who are using it > > and > > notice it being disabled. > > The 5 of them will notice it being disabled and then they'll realize > they either get a working kernel minus hibernation, or they get no > kernel at all because it doesn't compile.
Sure. But if we do the machine push thing they'll get both :) And I doubt it's 5, 2 is more likely. cheers _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
