From owner-freebsd-current Fri Jul 12 19:21:31 2002 Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C9E8737B400 for ; Fri, 12 Jul 2002 19:21:28 -0700 (PDT) Received: from mail.speakeasy.net (mail11.speakeasy.net [216.254.0.211]) by mx1.FreeBSD.org (Postfix) with ESMTP id 621F443E67 for ; Fri, 12 Jul 2002 19:21:28 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: (qmail 1680 invoked from network); 13 Jul 2002 02:21:27 -0000 Received: from unknown (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) by mail11.speakeasy.net (qmail-ldap-1.03) with DES-CBC3-SHA encrypted SMTP for ; 13 Jul 2002 02:21:27 -0000 Received: from laptop.baldwin.cx (laptop.baldwin.cx [192.168.0.4]) by server.baldwin.cx (8.11.6/8.11.6) with ESMTP id g6D2LP037999; Fri, 12 Jul 2002 22:21:25 -0400 (EDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.5.2 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <20020707111727.A77366@prism.flugsvamp.com> Date: Fri, 12 Jul 2002 22:21:35 -0400 (EDT) From: John Baldwin To: Jonathan Lemon Subject: Re: i386 trap code Cc: current@FreeBSD.ORG, David Schultz , David Xu Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On 07-Jul-2002 Jonathan Lemon wrote: > On Sat, Jul 06, 2002 at 11:59:50PM -0700, David Xu wrote: >> Jonthan, >> >> I just use DOS program as an example, for any program, if it wants to go >> into VM86 mode, it is very easy, just calls i386_vm86() to initailize its >> VM86 pcb extension, setups some memory area, then call sigreturn() to turn >> into VM86 mode. >> I think global in_vm86call flags is a bug under SMP, it creates a race >> condition. suppose this scenario: >> CPU A is running a simple VM86 code program. >> CPU B is running vm86_intcall() by some kernel driver (vesa module ?) >> CPU B set in_vm86call = 1 >> CPU A gets a fault trap. >> CPU A runs trap(), and find that in_vm86call is set and handles the trap >> as it is running vm86_intcall(), but it is not true and make a mess. > > Yes, as I mentioned earlier, the way the original vm86 bioscall worked > was to prevent an AST until the BIOS was done. This relied on the giant > lock for correctness, since we only allowed one CPU into the kernel at > once. There probably needs to be some work done for -current in this area. Since vm86_lock is a spin lock, you could possibly make in_vm86call per-cpu or you could just check the lock instead of the variable to fix this. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message