Re: [Qemu-devel] [Qemu-ppc] Qemu boot device precedence over nvram boot-device setting

[Benjamin Herrenschmidt <benh@au1.ibm.com>]

On Thu, 2012-09-27 at 11:51 +0200, Gleb Natapov wrote:

> Yes, forget about -boot. It is deprecated :) You should use bootindex
> (device property) to set boot priority. It constructs OF device path
> and passes it to firmware. There is nothing "blurry" about OF device
> path. 

Of course it is ;-) They are perfectly precise down to the device for
which qemu generates the device-tree ... and from there it requires the
firmware and qemu to both agree on how they are constructed, and it
becomes totally unpredictable once things like f-code drivers coming
from adapter ROMs enter the picture.

In fact, we can probably get them right down the the PCI device for PCI
(for which we don't currently construct the device nodes in qemu, but we
can 'guess'). And we can probably get the right unit address for vscsi,
virtio-scsi, etc... but that's about it.

> The problem is that it works reasonably well with legacy BIOS
> since it is enough to specify device to boot from, but with EFI (OF is
> the same I guess) it is not enough to point to a device to boot from,
> but you also need to specify a file you want to boot and this is where
> bootindex approach fails. If EFI would specify default file to boot from
> firmware could have used it, but EFI specifies it only for removable media
> (what media is not removable this days, especially with virtualization?).
> We can add qemu parameter to specify file to boot, but how users should
> know the name of the file?

Cheers,
Ben.