Re: [Qemu-devel] [PATCH 03/10] S390: Check Bootdevice Type

[Alexander Graf]

On 26.04.2013, at 18:01, Christian Borntraeger wrote:

> On 26/04/13 17:48, Alexander Graf wrote:
> 
>>> So I suggest to go with this patch and implement later on what we
>>> agree upon?
>> 
>> I don't see how having "first device we find" is any better than a 
>> rushed interface we need to agree on right before 1.5 hard freeze. 
> 
> Exactly, find first device isnt better ;-)
> See, the current code chooses the first subchannel that matches. This
> boils down to "a random disk" as soon as you have more than one.
> 
> With this patch the user can at least specify the devno of the disk.It
> even works out of the box with libvirt.
> 
> Let's just release 1.5 with the very simple one and then go for something 
> awesome in the next version.
> 
> Exactly - and having a list is more in the awesome area. Beiing able to
> specify the first disk and pass that in a register to the bios is of
> course not a full-features interface, but it works and can be changed.

My main concern is backwards compatibility. If we introduce a command line 
interface now, we have to support it forever. I'd rather only support one 
interface, rather than 2 out of which one is only legacy for 1.5 compatibility.

> Just to double check: do you agree that we can change the interface between
> ipl device and bios at any time?

I think that's a fair thing to do, though I wouldn't encourage it.


Alex