Re: [Qemu-devel] [PATCH 1/1] s390: IPL device for s390

[Alexander Graf]

On 08.05.2012, at 14:32, Christian Borntraeger wrote:

> On 04/05/12 20:12, Alexander Graf wrote:
>> 
>> On 04.05.2012, at 16:02, Christian Borntraeger wrote:
>> 
>>> On 04/05/12 16:00, Christian Borntraeger wrote:
>>>>>> An IPL (booting) on s390 of SCSI disks is done by a firmware component.
>>>>>> Lets implement this scheme as an qemu device that also allows to
>>>>>> configure the IPL like the HMC. We have a parameter iplid that
>>>>>> refers to a disk device and a load parm that specifies the entry
>>>>>> on the disk to be ipled. We also provide a default device
>>>>>> if no -device s390-ipl statement is given.
>>>>> 
>>>>> Any reason we can't do this in guest firmware code?
>>>> 
>>>> Conceptually guest firmware does not exist in the guest address space
>>>> on s390. It is separate in a storage area called HSA. 
>>>> (you could say the existing hardware is semi-hosted, you cant buy it bare 
>>>> metal.
>>>> Doing the boot code in guest address space will fail if the guest firmware
>>>> address  collides with the addresses specified by a bootmap.
>>> 
>>> Or in other words, this code is closer to the real s390 boxes.
>> 
>> Yeah, I see the point. I'd really like to get Anthony's comments on this one 
>> first though.
> 
> Right.
> 
> Anthony, this is the prototype of the IPL device that we have talked about 
> some weeks
> ago. Is an external device to do the IPL process for s390 still ok with you?

Even with an external IPL, we should still be able to detect that a guest 
provides its own virtio-zipl code that contains a boot menu and execute that 
instead of directly booting into the first entry, right?


Alex