From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ECC22C433EF for ; Fri, 26 Nov 2021 10:43:34 +0000 (UTC) Received: from localhost ([::1]:37694 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mqYhZ-0003eI-Q3 for qemu-devel@archiver.kernel.org; Fri, 26 Nov 2021 05:43:33 -0500 Received: from eggs.gnu.org ([209.51.188.92]:43400) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mqYgE-00026I-2a; Fri, 26 Nov 2021 05:42:10 -0500 Received: from gate.crashing.org ([63.228.1.57]:35768) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mqYgC-0006DW-0V; Fri, 26 Nov 2021 05:42:09 -0500 Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 1AQAbZLC013316; Fri, 26 Nov 2021 04:37:36 -0600 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 1AQAbW5R013308; Fri, 26 Nov 2021 04:37:32 -0600 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 26 Nov 2021 04:37:32 -0600 From: Segher Boessenkool To: =?iso-8859-1?Q?C=E9dric?= Le Goater Subject: Re: [OpenBIOS] Re: [RFC PATCH 0/2] QEMU/openbios: PPC Software TLB support in the G4 family Message-ID: <20211126103732.GP614@gate.crashing.org> References: <20211119134431.406753-1-farosas@linux.ibm.com> <87pmqpqknn.fsf@linux.ibm.com> <48c4262-ff7d-2897-9764-cadd98683e97@eik.bme.hu> <20211125093801.GM614@gate.crashing.org> <484dc989-71db-6273-e868-efaf2ad29fcf@kaod.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <484dc989-71db-6273-e868-efaf2ad29fcf@kaod.org> User-Agent: Mutt/1.4.2.3i Received-SPF: pass client-ip=63.228.1.57; envelope-from=segher@kernel.crashing.org; helo=gate.crashing.org X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Fabiano Rosas , danielhb413@gmail.com, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, openbios@openbios.org, david@gibson.dropbear.id.au Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi! On Fri, Nov 26, 2021 at 09:34:44AM +0100, Cédric Le Goater wrote: > On 11/25/21 10:38, Segher Boessenkool wrote: > >On Thu, Nov 25, 2021 at 01:45:00AM +0100, BALATON Zoltan wrote: > >>As for guests, those running on the said PowerMac G4 should have support > >>for these CPUs so maybe you can try some Mac OS X versions (or maybe > > > >OSX uses hardware pagetables. > > > >>MorphOS but that is not the best for debugging as there's no source > >>available nor any help from its owners but just to see if it boots it may > >>be sufficient, it should work on real PowerMac G4). > > > >I have no idea what MorphOS uses, but I bet HPT as well. That is > >because HPT is fastest in general. Software TLB reloads are good in > >special cases only; the most common is real-time OSes, which can use its > >lower guaranteed latency for some special address spaces (and can have a > >simpler address map in general). > > The support was added to QEMU knowing that Linux didn't handle soft TLBs. > And the commit says that it was kept disabled initially. I guess that was > broken these last years. Ah :-) So when was it enabled, do you know? > $ git show 7dbe11acd807 > commit 7dbe11acd807 > Author: Jocelyn Mayer > Date: Mon Oct 1 05:16:57 2007 +0000 > > Handle all MMU models in switches, even if it's just to abort because > of lack > of supporting code. > Implement 74xx software TLB model. > Keep 74xx with software TLB disabled, as Linux is not able to handle > TLB miss > on those processors. This is very specifically for 7450, not 7400, fwiw. 7400 is a nice core, while 7450 is ugly and asymmetric and unbalanced as hell. It can be faster though ;-) Segher