From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=44170 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1P5JQL-00059Y-Q9 for qemu-devel@nongnu.org; Mon, 11 Oct 2010 10:32:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1P5JNO-0001KA-Gp for qemu-devel@nongnu.org; Mon, 11 Oct 2010 10:29:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15480) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1P5JNO-0001Jx-9a for qemu-devel@nongnu.org; Mon, 11 Oct 2010 10:29:18 -0400 Date: Mon, 11 Oct 2010 16:29:14 +0200 From: Gleb Natapov Subject: Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios Message-ID: <20101011142914.GD28008@redhat.com> References: <20101011101855.GA25030@redhat.com> <4CB2F1F0.9010404@nsn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Disposition: inline Content-Transfer-Encoding: quoted-printable In-Reply-To: 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 On Mon, Oct 11, 2010 at 01:48:09PM +0100, Stefan Hajnoczi wrote: > On Mon, Oct 11, 2010 at 12:16 PM, Bernhard Kohl w= rote: > > 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=3Don 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. =9APCI 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 wh= at > >> EDD specification does. Describe disk as: > >> =9A =9A bus type (isa/pci), > >> =9A =9A address on a bus (16 bit base address for isa, b/s/f for pci) > >> =9A =9A device type (ATA/SCSI/VIRTIO) > >> =9A =9A device path (slave/master for ATA, LUN for SCSI, nothing for v= irtio) > >> > >> 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. >=20 > 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/ >=20 > Just wanted to post the link because it is related to the gPXE side of > this discussion. >=20 Don't we load gPXE for each NIC and seabios passes PCI device to boot from when it invokes one of them? -- Gleb.