From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=46379 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1P5LlD-0008Kk-S1 for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:02:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1P5LlC-0003mJ-EU for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:02:03 -0400 Received: from mail-qy0-f173.google.com ([209.85.216.173]:45163) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1P5LlC-0003mF-Bb for qemu-devel@nongnu.org; Mon, 11 Oct 2010 13:02:02 -0400 Received: by qyk36 with SMTP id 36so1142732qyk.4 for ; Mon, 11 Oct 2010 10:02:01 -0700 (PDT) Message-ID: <4CB34306.4040501@codemonkey.ws> Date: Mon, 11 Oct 2010 12:01:58 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios References: <20101011101855.GA25030@redhat.com> <4CB2F1F0.9010404@nsn.com> <20101011142914.GD28008@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Bernhard Kohl , seabios@seabios.org, qemu-devel@nongnu.org, Gleb Natapov 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? Regards, Anthony Liguori > Stefan > >