From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1Nex7v-0004O5-2W for qemu-devel@nongnu.org; Tue, 09 Feb 2010 15:56:07 -0500 Received: from [199.232.76.173] (port=39534 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Nex7t-0004Nx-MP for qemu-devel@nongnu.org; Tue, 09 Feb 2010 15:56:05 -0500 Received: from Debian-exim by monty-python.gnu.org with spam-scanned (Exim 4.60) (envelope-from ) id 1Nex7s-00057y-4c for qemu-devel@nongnu.org; Tue, 09 Feb 2010 15:56:05 -0500 Received: from mail.gmx.net ([213.165.64.20]:47150) by monty-python.gnu.org with smtp (Exim 4.60) (envelope-from ) id 1Nex7q-00057U-6n for qemu-devel@nongnu.org; Tue, 09 Feb 2010 15:56:03 -0500 Message-ID: From: "Sebastian Herbszt" References: <4B6FE4BD.5010304@siemens.com> <8D0A564F20EB4421B2CC199C47C63EA6@FSCPC> <4B70615D.2080406@siemens.com> <20100209005110.GC18282@morn.localdomain> In-Reply-To: <20100209005110.GC18282@morn.localdomain> Date: Tue, 9 Feb 2010 21:47:25 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: Seabios dislikes -M isapc List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin O'Connor , Jan Kiszka Cc: qemu-devel Kevin O'Connor wrote: > On Mon, Feb 08, 2010 at 08:09:17PM +0100, Jan Kiszka wrote: >> Sebastian Herbszt wrote: >> > Jan Kiszka wrote: >> >> Hi, >> >> >> >> Seabios seems to have some assumptions built in that break when -M isapc >> >> is selected. Is this supposed to work or is isapc about to die? >> > >> > SeaBIOS doesn't POST if the F-segment is not writeable [1]. A possible, but IMO >> > wrong fix was posted on the list [2]. >> > >> > [1] http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01188.html >> > [2] http://lists.gnu.org/archive/html/qemu-devel/2009-12/msg00445.html >> > >> >> Indeed, [2] makes it work again. >> >> But taking away IO_MEM_ROM really looks like a lazy workaround. I don't >> know how much Seabios needs to write - can't it use normal RAM for this? > > Handling a read-only f-segment in SeaBIOS would result in significant > code complexity, and some features (like smbios) couldn't be made to > work at all. > > I believe it would be far simpler to add a mechanism for > locking/unlocking the f-segment in non-pci mode than it would be to > make seabios work with a read-only f-segment. > > Finally, in the normal pci enabled case, both SeaBIOS and bochs bios > will lock the f-segment regardless of how it starts. So, the patch at > [1] is pretty harmless and it leads to an overall simplification. On the other hand the F-segment will stay unlocked on isapc. Bochs BIOS comes in two flavours: BIOS-bochs-legacy (rombios) and BIOS-bochs-latest (rombios + rombios32). None of both requires the F-segment to be writeable. BIOS-bochs-legacy doesn't put anything there. BIOS-bochs-latest puts some tables (e.g. mp, acpi) there unless BX_USE_EBDA_TABLES is set. - Sebastian