From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=40783 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q1jpT-0003S6-Nl for qemu-devel@nongnu.org; Mon, 21 Mar 2011 14:27:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q1jpS-0006Md-FS for qemu-devel@nongnu.org; Mon, 21 Mar 2011 14:27:47 -0400 Received: from mail-gx0-f174.google.com ([209.85.161.174]:37895) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q1jpS-0006MO-7p for qemu-devel@nongnu.org; Mon, 21 Mar 2011 14:27:46 -0400 Received: by gxk21 with SMTP id 21so2996710gxk.33 for ; Mon, 21 Mar 2011 11:27:45 -0700 (PDT) Message-ID: <4D87989D.70005@codemonkey.ws> Date: Mon, 21 Mar 2011 13:27:41 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] OVMF, SeaBIOS & non-CSM based legacy boot References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jordan Justen Cc: qemu-devel On 03/21/2011 01:14 PM, Jordan Justen wrote: > This weekend I spent some time working on loading SeaBIOS from OVMF to > start a legacy boot. I was able to get x86& x86-64 Linux to legacy > boot using this method. > > Unfortunately, (I think) it is not nearly as nice a having a true CSM. > Basically, you have to decide at some point in the OVMF boot that you > want to legacy boot, and once you start SeaBIOS running, OVMF/UEFI Interesting. How much time does OVMF add to the total boot time when taking this approach? > will never be in the picture again (until system reset). > > Contrast this to using a CSM where you can: > * Load a legacy option ROM (vbios, or disk rom), > and use it during a UEFI boot Is there gPXE for UEFI yet? Other than that, this probably matters most of with device passthrough. I think this is a limitation we could live with in the not-to-short term though. > * Fail a legacy boot, and potentially return back to UEFI if it fails. > (Not in all cases, if the failed boot alters the system state significantly) I think the most typical use-case here is -boot cd or -boot dc. From what I can tell, EFI support El Torito so it wouldn't be necessary to involve BIOS to handle booting from CDROMs. Is that correct? > * Specify via UEFI the boot process which disk to legacy boot in the CSM I'm sure this is workable. > So, would this be valuable (in the short term) to help move forward > QEMU's usage of OVMF and add UEFI support? Or would QEMU require true > CSM support? I think this certainly helps make the discussion more concrete. I don't see any show stoppers here. Regards, Anthony Liguori > Thanks, > > -Jordan >