linux-kernel - Re: Missing operand for tlbie instruction on Power7

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Message-ID: <20151007071911.GA31002@gate.crashing.org>
Date:	Wed, 7 Oct 2015 02:19:11 -0500
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Laura Abbott <labbott@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Missing operand for tlbie instruction on Power7

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 :-)

> 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.

Segher
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