From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51692) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zo8tm-0002je-Nh for qemu-devel@nongnu.org; Mon, 19 Oct 2015 07:46:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zo8ti-0008R6-O3 for qemu-devel@nongnu.org; Mon, 19 Oct 2015 07:46:42 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:9125) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zo8ti-0008Qy-JS for qemu-devel@nongnu.org; Mon, 19 Oct 2015 07:46:38 -0400 Date: Mon, 19 Oct 2015 12:44:01 +0100 From: Stefano Stabellini In-Reply-To: <1445254058.13733.39.camel@redhat.com> Message-ID: References: <561D2966.9070007@m2r.biz> <561D3513.8060005@redhat.com> <562160CC.8050204@redhat.com> <1445254058.13733.39.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Subject: Re: [Qemu-devel] Question about xen disk unplug support for ahci missed in qemu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerd Hoffmann Cc: Stefano Stabellini , "qemu-devel@nongnu.org" , "xen-devel@lists.xen.org" , Fabio Fantoni , Anthony.Perard@citrix.com, John Snow On Mon, 19 Oct 2015, Gerd Hoffmann wrote: > Hi, > > > > I'm trying to follow this discussion as best as I am able, but my lack > > > of experience with Xen prevents me from really participating in a > > > meaningful way. > > > > > > (I see that Laszlo is still discussing some CD-ROM issues with Fabio > > > which may be of interest to me...) > > > > > > At any rate, I won't be authoring any Xen-specific hacks to the AHCI > > > device, but I do have plans to implement hot-plugging emulation as per > > > the AHCI spec. Perhaps this is sufficient for the Xen layer, but someone > > > else will need to author the appropriate glue code. > > > > > > If "real" hot-plugging is not sufficient, we'll need to discuss further, > > > preferably over some RFC patches. > > > > That's fine. AHCI hot-plugging would go a long way and once we have > > that, the rest is easy. > > Can we get some more background on this? > > IIRC the IDE bits are needed to boot hvm guests, which goes like this: > > (1) boot disk is hooked up using both xenbus and ide. > (2) seabios boots using ide. > (3) linux kernel activates xenbus, at which point qemu zaps the ide > disks to avoid the disk being present twice in the system. > > Correct? > > Do we really want repeat this exercise for AHCI? Alot has changed since > this boot hack for ide was added ... > > As far I know OVMF has xenbus drivers, so OVMF should already boot xen > guests just fine without this, correct? I agree with you that the current unplug in nasty. Also I don't care much about AHCI, in fact I don't think we should be spending efforts into making that scenario work better. I think we should be working on OVMF instead and fix the bug about empty cdrom drives reported by Fabio. > Can we just have xenbus drivers for seabios too? seabios can run disk > drivers in 32bit mode meanwhile, so this should not be as difficult any > more as it used to be. Sure, I would be happy to see that happen, but I won't be working on it.