From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49039) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TTqU2-0006wz-1Q for qemu-devel@nongnu.org; Thu, 01 Nov 2012 04:50:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TTqU1-0002nz-1z for qemu-devel@nongnu.org; Thu, 01 Nov 2012 04:50:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20644) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TTqU0-0002nq-PS for qemu-devel@nongnu.org; Thu, 01 Nov 2012 04:50:36 -0400 Message-ID: <509237D5.1040602@redhat.com> Date: Thu, 01 Nov 2012 09:50:29 +0100 From: Gerd Hoffmann MIME-Version: 1.0 References: <87k3u82f7b.fsf@blackfin.pond.sub.org> <509000E8.9090703@redhat.com> In-Reply-To: <509000E8.9090703@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] On block interface types in general, IF_AHCI in particular List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Kevin Wolf , Anthony Liguori , qemu-devel@nongnu.org, Jason Baron , Alexander Graf , Markus Armbruster , Stefan Hajnoczi Hi, > The main drawback of if=ahci is, as pointed out by Markus, that you > would have to provide both controllers on-board. I think a real ICH9 > has the compatibility IDE controller on a separate PCI address from the > SATA controller, so creating both of them is not really out of question. I think this can be turned on and off by the bios. When configured in ahci mode there is no IDE controller. It shows up when you switch to IDE in the bios though. [ side note: I suspect this could be the reason why the *BSDs don't work with our AHCI emulation, might be they try to look at the ich9-specific registers which control ahci/ide mode and we don't emulate that properly. ] > Obvious disadvantage, it would depart from real hardware. Linux should > not care, not sure about SeaBIOS and Windows. > At the same time, if all we want is a quick way to switch between IDE > and AHCI, we could just use machine types. So another proposal is to > have two machine types, one for ICH9-IDE (pc, the default), one for > ICH9-AHCI (q35), one for PIIX3-IDE (piix3). Each QEMU release would add > (up to) three machine types. I'd tend to just point people to pc-piix for guests too old to be shipped with ahci drivers and be done with it. Chances are high that they have more issues with q35 anyway. cheers, Gerd