From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39248) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dHuSN-0000ws-Dc for qemu-devel@nongnu.org; Mon, 05 Jun 2017 12:02:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dHuSK-0005WW-CD for qemu-devel@nongnu.org; Mon, 05 Jun 2017 12:02:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38262) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dHuSK-0005VZ-6C for qemu-devel@nongnu.org; Mon, 05 Jun 2017 12:02:12 -0400 Date: Mon, 5 Jun 2017 19:02:00 +0300 From: "Michael S. Tsirkin" Message-ID: <20170605185815-mutt-send-email-mst@kernel.org> References: <2ff62b03-d71b-93c4-79bf-10682b229758@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2ff62b03-d71b-93c4-79bf-10682b229758@redhat.com> Subject: Re: [Qemu-devel] allocation zone extensions for the firmware linker/loader List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: SeaBIOS devel list , qemu devel list , edk2-devel-ml01 , Kevin O'Connor , Ard Biesheuvel , Ben Warren , Dongjiu Geng , Igor Mammedov , "Jordan Justen (Intel address)" , "Leif Lindholm (Linaro address)" , Shannon Zhao , Stefan Berger , Xiao Guangrong , "Dr. David Alan Gilbert" , Gerd Hoffmann On Sat, Jun 03, 2017 at 09:36:23AM +0200, Laszlo Ersek wrote: > On 06/02/17 17:45, Laszlo Ersek wrote: > > > The patches can cause linker/loader breakage when old firmware is booted > > on new QEMU. However, that's no problem (it's nothing new), the next > > release of QEMU should bundle the new firmware binaries as always. > > Dave made a good point (which I should have realized myself, really!), > namely if you launch old fw on old qemu, then migrate the guest to a new > qemu and then reboot the guest on the target host, within the migrated > VM, things will break. > > So that makes this approach dead in the water. > > Possible mitigations I could think of: > - Make it machine type dependent. Complicated (we don't usually bind > ACPI generation to machine types) and wouldn't help existing devices. > - Let the firmware negotiate these extensions. Very complicated (new > fw-cfg files are needed for negotiation) and wouldn't help existing devices. This last option *shouldn't* be complicated. If it is something's wrong. Maybe we made a mistake when we added etc/smi/*features*. It's not too late to move these to etc/*features* for new machine types if we want to and if you can do the firmware work. Then you'd just take out a bit and be done with it. I don't insist on doing the ACPI thing now but I do think infrastructure for negotiating extensions should be there. -- MST