From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with archive (Exim 4.43) id 1N9MON-0005lA-Ff for mharc-grub-devel@gnu.org; Sat, 14 Nov 2009 12:26:31 -0500 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1N9MOK-0005hz-By for grub-devel@gnu.org; Sat, 14 Nov 2009 12:26:28 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1N9MOF-0005hK-4q for grub-devel@gnu.org; Sat, 14 Nov 2009 12:26:27 -0500 Received: from [199.232.76.173] (port=58635 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N9MOE-0005h0-Os for grub-devel@gnu.org; Sat, 14 Nov 2009 12:26:22 -0500 Received: from xvm-190-8.ghst.net ([217.70.190.8]:52049 helo=aybabtu.com) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1N9MOE-0004eb-9O for grub-devel@gnu.org; Sat, 14 Nov 2009 12:26:22 -0500 Received: from [192.168.10.10] (helo=thorin) by aybabtu.com with esmtp (Exim 4.69) (envelope-from ) id 1N9MOA-0003UE-3y for grub-devel@gnu.org; Sat, 14 Nov 2009 18:26:19 +0100 Received: from rmh by thorin with local (Exim 4.69) (envelope-from ) id 1N9MO3-00068J-5m for grub-devel@gnu.org; Sat, 14 Nov 2009 18:26:11 +0100 Date: Sat, 14 Nov 2009 18:26:11 +0100 From: Robert Millan To: The development of GNU GRUB Message-ID: <20091114172611.GA18813@thorin> References: <20091114105926.GA9262@aybabtu.com> <4AFEA700.4030204@gmail.com> <20091114153822.GB7084@thorin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091114153822.GB7084@thorin> Organization: free as in freedom X-Message-Flag: Worried about Outlook viruses? Switch to Thunderbird! www.mozilla.com/thunderbird X-Debbugs-No-Ack: true User-Agent: Mutt/1.5.18 (2008-05-17) X-detected-operating-system: by monty-python.gnu.org: GNU/Linux 2.6 (newer, 3) Subject: Re: gate A20 and i386-qemu port X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: The development of GNU GRUB List-Id: The development of GNU GRUB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Nov 2009 17:26:28 -0000 On Sat, Nov 14, 2009 at 04:38:22PM +0100, Robert Millan wrote: > > Following code can check A20: > > *((volatile grub_uint8_t *) 0x200000) = 0; > > *((volatile grub_uint8_t *) 0x300000) = 1; > > if (*((volatile grub_uint8_t *) 0x200000)) > > grub_printf ("Expect bugs\n"); > > else > > grub_printf ("You're safe\n"); > > Yeah, in fact we have gate_a20_check_state() to check for this, but only > in i386-pc. > > I find it surprising that i386-qemu works at all without it. I guess it > only works because the high mem area that would overlap with our code in > 0x8200 is never used. > > I'll look into this... It appears that QEMU hardware already starts with A20 enabled. I suppose it's bochsbios who disables it. In any case, I made my vbe-on-coreboot branch enable it. Unfortunately, this wasn't the cause that prevented vbetest/vbeinfo from working :-/ -- Robert Millan The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and how) you may access your data; but nobody's threatening your freedom: we still allow you to remove your data and not access it at all."