From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51415) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZoDhl-0003mc-Qu for qemu-devel@nongnu.org; Mon, 19 Oct 2015 12:54:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZoDhg-0007ql-O2 for qemu-devel@nongnu.org; Mon, 19 Oct 2015 12:54:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50160) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZoDhg-0007qd-I8 for qemu-devel@nongnu.org; Mon, 19 Oct 2015 12:54:32 -0400 References: <561D2966.9070007@m2r.biz> <561D3513.8060005@redhat.com> <562160CC.8050204@redhat.com> <1445254058.13733.39.camel@redhat.com> From: John Snow Message-ID: <56252046.7070508@redhat.com> Date: Mon, 19 Oct 2015 12:54:30 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit 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: Stefano Stabellini , Gerd Hoffmann Cc: Anthony.Perard@citrix.com, Fabio Fantoni , "qemu-devel@nongnu.org" , "xen-devel@lists.xen.org" On 10/19/2015 07:44 AM, Stefano Stabellini wrote: > 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. > OVMF and AHCI go hand in hand here from my viewpoint. I'm happy to debug any OVMF+SATA/AHCI problems that are reported. Last I saw, Laszlo asked Fabio for some more information on this problem, so I am waiting for that information to start work on that issue. Thanks, --js > >> 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. >