Re: Missing operand for tlbie instruction on Power7

On Wed, 2015-10-07 at 20:15 -0400, Josh Boyer wrote:

On Wed, Oct 7, 2015 at 8:10 PM, Michael Ellerman [off-list ref] wrote:

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On Wed, 2015-10-07 at 10:31 -0400, Josh Boyer wrote:

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On Wed, Oct 7, 2015 at 5:13 AM, Michael Ellerman [off-list ref] wrote:

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On Wed, 2015-10-07 at 02:19 -0500, Segher Boessenkool wrote:

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On Wed, Oct 07, 2015 at 05:00:49PM +1100, Michael Ellerman wrote:

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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.

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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 :)

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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