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

[Alexander Graf]

On 27.09.2012, at 11:21, Avik Sil wrote:

> Hi,
> 
> We would like to get a method to boot from devices provided in -boot 
> arguments in qemu when the 'boot-device' is set in nvram for pseries machine. 
> I mean the boot device specified in -boot should get a precedence over the 
> 'boot-device' specified in nvram.
> 
> At the same time, when -boot is not provided, i.e., the default boot order 
> "cad" is present, the device specified in nvram 'boot-device' should get 
> precedence if it is set.
> 
> What should be the elegant way to implement this requirement? Suggestions 
> welcome.

I would like to see us reuse the same methods that all the other platforms are 
using (x86, OpenBIOS PPC, etc). On these machines we have fw_cfg which can tell 
firmware configuration bits that the hypervisor can pass in.

However, using MMIO might be a bad idea for that one, since 970 HV KVM can not 
handle that. So how about adding a hypercall based fw_cfg interface in parallel 
to the current MMIO/PIO based one?

That way we could reuse almost all of the existing infrastructure.


Alex