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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4D6DC4338F for ; Sun, 25 Jul 2021 10:13:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8ED4360E78 for ; Sun, 25 Jul 2021 10:13:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230479AbhGYJca (ORCPT ); Sun, 25 Jul 2021 05:32:30 -0400 Received: from cynthia.allandria.com ([50.242.82.17]:42350 "EHLO cynthia.allandria.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230472AbhGYJc3 (ORCPT ); Sun, 25 Jul 2021 05:32:29 -0400 Received: from flar by cynthia.allandria.com with local (Exim 4.84_2) (envelope-from ) id 1m7b7t-0001kc-HR; Sun, 25 Jul 2021 03:12:53 -0700 Date: Sun, 25 Jul 2021 03:12:53 -0700 From: Brad Boyer To: Michael Schmitz Cc: Andreas Schwab , "Eric W. Biederman" , geert@linux-m68k.org, linux-arch@vger.kernel.org, linux-m68k@lists.linux-m68k.org, torvalds@linux-foundation.org Subject: Re: [PATCH v4 0/3] m68k: Improved switch stack handling Message-ID: <20210725101253.GA6096@allandria.com> References: <87h7gopvz2.fsf@disp2133> <328e59fb-3e8c-e4cd-06b4-1975ce98614a@gmail.com> <877dhio13t.fsf@disp2133> <12992a3c-0740-f90e-aa4e-1ec1d8ea38f6@gmail.com> <87tukkk6h3.fsf@disp2133> <87eebn7w7y.fsf@igel.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Sun, Jul 25, 2021 at 07:44:11PM +1200, Michael Schmitz wrote: > Am 25.07.2021 um 00:05 schrieb Andreas Schwab: > >On Jul 24 2021, Michael Schmitz wrote: > > > >>According to my understanding, you can't get a F-line exception on > >>68040. > > > >The F-line exception vector is used for all FPU illegal and > >unimplemented insns. > > Thanks - now from my reading of the fpsp040 code (which has mislead me in > the past), it would seem that operations like sin() and exp() ought to raise > that exception then. I don't see that in ARAnyM. Yes, according to the 68040 user's manual, unimplemented and illegal F-line instructions trigger the standard F-line exception vector (11) but have separate stack frame formats so the fpsp040 code gets some extra data. The CPU does a bunch of the prep work so that part doesn't need to be emulated in software. The ARAnyM docs appear to claim a strange combination that wouldn't exist in hardware by implementing a full 68882 instead of the limited subset found on a real 68040. Strangely, that might have been easier to implement. However, it would also completely bypass any use of fpsp040. Brad Boyer flar@allandria.com