Re: [Qemu-devel] [PATCH 12/13] Add zipl bootloader interpreter

[Alexander Graf]

On 24.11.2009, at 20:26, Anthony Liguori wrote:

> Alexander Graf wrote:
>> On 24.11.2009, at 19:53, Anthony Liguori wrote:
>> 
>>  
>>> Alexander Graf wrote:
>>>    
>>>> The default bootloader on S390 is zipl. Because we don't emulate normal 
>>>> S390
>>>> hardware we need to write our own parser for the bootloader configuration,
>>>> so we can boot off real hard disks.
>>>> 
>>>> This patch adds a pretty simple implementation of such an interpreter. It 
>>>> only
>>>> supports 512 bytes sector sizes, always boots the default entry and doesn't
>>>> work with reboots yet. But it's better than nothing.
>>>>       
>>> This is a bit unfortunate.  Wouldn't it be better to write a custom version 
>>> of zipl that ran in the guest?
>>>    
>> 
>> Yeah, I've been struggling quite a bit with this myself. Writing a custom 
>> version that runs in the guest means we have to create
>> 
>> 1) extboot
>> 2) input backdoor
>> 
>> Or implement virtio in that custom version. That sounds like a pretty huge 
>> project.
>> 
>> So I decided to go for the easy way for now and hopefully migrate to an 
>> in-guest version later.
>>  
> 
> Can't you just use kboot?
> 
> Use a kernel loader to load the kboot module/initrd, include kboot as our 
> firmware, then let kboot do the magic to launch the real linux kernel from 
> disk.

Hm, so we'd have to rely on kexec working properly? I've seen how badly that 
turned out on the PS3. I guess I'd rather write a virtio implementation :-).

Alex