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[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios
From: |
Kevin O'Connor |
Subject: |
[Qemu-devel] Re: [SeaBIOS] [RFC] Passing boot order from qemu to seabios |
Date: |
Mon, 11 Oct 2010 20:08:08 -0400 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Mon, Oct 11, 2010 at 12:18:55PM +0200, 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)
That makes sense to me.
We could update SeaBIOS to give a short unique name to every BEV and
BCV it finds based on the path to the device. (For example, something
like "address@hidden:address@hidden", "address@hidden:5678",
"address@hidden:13.0",
"address@hidden:13.0".) Then qemu could pass in (via fw_cfg) a list of names
that the user wishes to boot from. SeaBIOS can then prioritizes those
devices it finds that are also in the fw_cfg list.
> Will it cover all use cased? Any other ideas? Any ideas about qemu
> command line syntax? May be somebody whats to implement it? :)
As for qemu command line - maybe just use the current ",boot=on"
syntax, and have qemu map it into a "path name" for seabios?
-Kevin
- Re: [Qemu-devel] [RFC] Passing boot order from qemu to seabios, (continued)
- 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 <=