From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751538AbbJHAKk (ORCPT ); Wed, 7 Oct 2015 20:10:40 -0400 Received: from ozlabs.org ([103.22.144.67]:46032 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750778AbbJHAKj (ORCPT ); Wed, 7 Oct 2015 20:10:39 -0400 Message-ID: <1444263036.31685.2.camel@ellerman.id.au> Subject: Re: Missing operand for tlbie instruction on Power7 From: Michael Ellerman To: Josh Boyer Cc: Segher Boessenkool , Laura Abbott , Paul Mackerras , "linuxppc-dev@lists.ozlabs.org" , Linux Kernel Mailing List Date: Thu, 08 Oct 2015 11:10:36 +1100 In-Reply-To: References: <560EA623.1040300@redhat.com> <1444102518.16909.3.camel@ellerman.id.au> <56141237.2040403@redhat.com> <1444197649.6794.7.camel@ellerman.id.au> <20151007071911.GA31002@gate.crashing.org> <1444209210.19375.1.camel@ellerman.id.au> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11-0ubuntu3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2015-10-07 at 10:31 -0400, Josh Boyer wrote: > On Wed, Oct 7, 2015 at 5:13 AM, Michael Ellerman 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. cheers