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[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios
From: |
Gleb Natapov |
Subject: |
[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios |
Date: |
Mon, 11 Oct 2010 17:52:54 +0200 |
On Mon, Oct 11, 2010 at 05:42:30PM +0200, Avi Kivity wrote:
> On 10/11/2010 05:39 PM, Gleb Natapov wrote:
> >On Mon, Oct 11, 2010 at 05:09:22PM +0200, Avi Kivity wrote:
> >> On 10/11/2010 12:18 PM, Gleb Natapov wrote:
> >> >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? Any ideas about qemu
> >> >command line syntax? May be somebody whats to implement it? :)
> >>
> >> Instead of fwcfg, we should store the boot order in the bios. This
> >> allows seabios to implement persistent boot selection and control
> >> boot order from within the guest.
> >>
> >It is not "instead of" it is in a best case "in addition too". First of
> >all seabios does not have persistent storage currently and second I much
> >prefer specifying boot device from command line instead of navigating
> >bios menus. That what we have to do on real HW because there is not
> >other way to do it, but in virtualization we can do better.
>
> Ok. So fwcfg will have an option "do your default thing" which the
> bios can take as a hint to look in cmos memory.
>
Definitely. If qemu does not provide any info about boot order default
logic should be used.
--
Gleb.
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, (continued)
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Gleb Natapov, 2010/10/11
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Stefan Hajnoczi, 2010/10/11
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Gleb Natapov, 2010/10/11
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Anthony Liguori, 2010/10/11
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Gleb Natapov, 2010/10/11
- Re: [SeaBIOS] [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Kevin O'Connor, 2010/10/11
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, Stefan Hajnoczi, 2010/10/12
[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios, Avi Kivity, 2010/10/11
[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios, Kevin O'Connor, 2010/10/11