From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=44965 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1P5Lnb-0001SS-6K for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:04:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1P5LnZ-0004Dn-Oh for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:04:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:31421) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1P5LnZ-0004Dj-Hg for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:04:29 -0400 Date: Mon, 11 Oct 2010 19:04:25 +0200 From: Gleb Natapov Subject: Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios Message-ID: <20101011170425.GH28008@redhat.com> References: <20101011101855.GA25030@redhat.com> <4CB2F1F0.9010404@nsn.com> <20101011142914.GD28008@redhat.com> <4CB34306.4040501@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4CB34306.4040501@codemonkey.ws> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Stefan Hajnoczi , seabios@seabios.org, qemu-devel@nongnu.org, Bernhard Kohl On Mon, Oct 11, 2010 at 12:01:58PM -0500, Anthony Liguori wrote: > On 10/11/2010 10:52 AM, Stefan Hajnoczi wrote: > >2010/10/11 Gleb Natapov: > >>On Mon, Oct 11, 2010 at 01:48:09PM +0100, Stefan Hajnoczi wrote: > >>>On Mon, Oct 11, 2010 at 12:16 PM, Bernhard Kohl wrote: > >>>>Am 11.10.2010 12:18, schrieb ext Gleb Natapov: > >>>>>Currently if VM is started with multiple disks it is almost impossible to > >>>>>guess which one of them will be used as boot device especially if there > >>>>>is a mix of ATA/virtio/SCSI devices. Essentially BIOS decides the order > >>>>>and without looking into the code you can't tell what the order will > >>>>>be (and in qemu-kvm if boot=on is used it brings even more havoc). We > >>>>>should allow fine-grained control of boot order from qemu command line, > >>>>>or as a minimum control what device will be used for booting. > >>>>> > >>>>>To do that along with inventing syntax to specify boot order on qemu > >>>>>command line we need to communicate boot order to seabios via fw_cfg > >>>>>interface. For that we need to have a way to unambiguously specify a > >>>>>disk from qemu to seabios. PCI bus address is not enough since not all > >>>>>devices are PCI (do we care about them?) and since one PCI device may > >>>>>control more then one disk (ATA slave/master, SCSI LUNs). We can do what > >>>>>EDD specification does. Describe disk as: > >>>>> bus type (isa/pci), > >>>>> address on a bus (16 bit base address for isa, b/s/f for pci) > >>>>> device type (ATA/SCSI/VIRTIO) > >>>>> device path (slave/master for ATA, LUN for SCSI, nothing for virtio) > >>>>> > >>>>>Will it cover all use cased? Any other ideas? > >>>>I think this also applies to network booting via gPXE. Usually our VMs > >>>>have 4 NICs, mixed virtio-net and PCI pass-through. 2 of the NICs shall > >>>>be used for booting, even if there are hard disks or floppy disks > >>>>connected. This scenario is currently almost impossible to configure. > >>>Here is a gPXE to support fw_cfg. You can pass gPXE script files from > >>>the host to gPXE inside the guest. This means you can boot specific > >>>NICs: > >>>http://patchwork.ozlabs.org/patch/43777/ > >>> > >>>Just wanted to post the link because it is related to the gPXE side of > >>>this discussion. > >>> > >>Don't we load gPXE for each NIC and seabios passes PCI device to boot from > >>when it invokes one of them? > >SeaBIOS may do that but gPXE internally just probes all PCI devices. > >It does not take advantage of the PCI bus/addr/fn that was passed to > >the option ROM. A gPXE instance will try booting from each available > >NIC in sequence. > > It still registers a BEV entry though, no? > > Does it at least try to boot from the PCI bus/addr/fn of the > selected BEV entry? > I think so. Kevin will know for sure. -- Gleb.