From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52935) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agUYE-0008Tl-Jc for qemu-devel@nongnu.org; Thu, 17 Mar 2016 05:49:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1agUYD-0007AX-G5 for qemu-devel@nongnu.org; Thu, 17 Mar 2016 05:49:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44522) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agUYD-0007AP-Al for qemu-devel@nongnu.org; Thu, 17 Mar 2016 05:49:05 -0400 References: <20160316181541.GG12454@HEDWIG.INI.CMU.EDU> <56E9A75D.60603@redhat.com> <1458204143.26199.8.camel@redhat.com> From: Laszlo Ersek Message-ID: <56EA7D8E.7000000@redhat.com> Date: Thu, 17 Mar 2016 10:49:02 +0100 MIME-Version: 1.0 In-Reply-To: <1458204143.26199.8.camel@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] vl.c: disallow command line fw cfg without opt/ List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: pbonzini@redhat.com, "Gabriel L. Somlo" , qemu-devel@nongnu.org, armbru@redhat.com, mst@redhat.com On 03/17/16 09:42, Gerd Hoffmann wrote: > Hi, > >>> Having a mis-use of this feature become "institutionalized" over time was >>> seen as a low/negligible risk at the time. Do we have any new reasons >>> to worry about it ? >> >> OVMF uses this feature for a few flags. They are all called >> "opt/ovmf/...". I followed the advice in "docs/specs/fw_cfg.txt" (which >> shouldn't be surprising since I seem to have reviewed every patch for >> that file): > > seabios has a few flags too, in etc/. Some of them are supported > directly by qemu (such as setting the boot menu delay). I forgot to confirm: clearly, when some flag already exists on which we can foist, kicking and screaming, a somewhat similar interpretation in OVMF, we do that without inventing a new flag. The boot menu delay is like this. Namely, if you set "-boot menu=on,splash-time=5000", you will get a progress bar for five seconds before auto-booting the otherwise relevant boot option. The QEMU manual documents the -boot option as guest firmware-specific, and OVMF operates with that in mind -- support what it can, as closely it can. Thanks Laszlo > Others are not, > and I'd like to be able to use -fw_cfg for them for testing/debugging > (any use cases beyond that should be supported by adding a less obscure > way to set them to qemu, similar to the boot delay). > > Oh, and that'll most likely be more seabios testing than qemu testing, > so why require me build a special qemu version for that? > > On the ovmf flags: What kind of flags are there? Anything a normal > user might want to set? > > cheers, > Gerd >