Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 1 Aug 2002 13:04:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 1 Aug 2002 13:04:00 -0400 Received: from daimi.au.dk ([130.225.16.1]:40602 "EHLO daimi.au.dk") by vger.kernel.org with ESMTP id ; Thu, 1 Aug 2002 13:04:00 -0400 Message-ID: <3D496A24.4E134ED5@daimi.au.dk> Date: Thu, 01 Aug 2002 19:04:36 +0200 From: Kasper Dupont Organization: daimi.au.dk X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.4.9-31smp i686) X-Accept-Language: en MIME-Version: 1.0 To: "Maciej W. Rozycki" CC: Alan Cox , root@chaos.analogic.com, stas.orel@mailcity.com, linux-kernel@vger.kernel.org Subject: Re: [patch] vm86: Clear AC on INT References: Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1787 Lines: 39 "Maciej W. Rozycki" wrote: > > On Thu, 1 Aug 2002, Kasper Dupont wrote: > > > Ehrm, that wasn't my point. My point was that if the feature exist > > in virtual 86 mode but not in real mode, the kernel should prevent > > it from being used in virtual 86 mode because it is supposed to > > emulate real mode. > > The mode is supposed to emulate an 8086 which doesn't have the flag. OK, but if it is only supposed to emulate an 8086 shouldn't it have trapped on every instruction not existing on 8086? It doesn't and that is quite fortunate, because we can then use it for other purposes namely runing software that expects to have the entire computer for itself in a multitasking environment. However it seems no matter how we do it, what is emulated will not work exactly like any CPU in real mode. > Any "real mode" code that operates on the AC flag must have been > created after i386 was released as it requires 32-bit instructions. Hence > it has to be prepared to deal with the vm86 mode. That does make some sense, but not all software written for i386 and later processors does deal with vm86 in the desired way. Some software was only intended for real mode when being written, but we might now want to run it in virtual 86 mode. Thanks to emm386 we probably don't see many DOS programs not working in virtual 86 mode, but emm386 itself plain refuses to load in virtual 86 mode. -- Kasper Dupont -- der bruger for meget tid p? usenet. For sending spam use mailto:razrep@daimi.au.dk or mailto:mcxumhvenwblvtl@skrammel.yaboo.dk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/