Re: [Qemu-devel] [PATCH v5 05/12] s390-ccw: move auxiliary IPL data to separate location

[Viktor Mihajlovski <mihajlov@linux.vnet.ibm.com>]

On 06.02.2018 10:45, Christian Borntraeger wrote:
> On 02/05/2018 09:57 PM, Collin L. Walling wrote:
>> The s390-ccw firmware needs some information in support of the
>> boot process which is not available on the native machine.
>> Examples are the netboot firmware load address and now the
>> boot menu parameters.
>>
>> While storing that data in unused fields of the IPL parameter block
>> works, that approach could create problems if the parameter block
>> definition should change in the future. Because then a guest could
>> overwrite these fields using the set IPLB diagnose.
>>
>> In fact the data in question is of more global nature and not really
>> tied to an IPL device, so separating it is rather logical.
>>
>> This commit introduces a new structure to hold firmware relevant
>> IPL parameters set by QEMU. The data is stored at location 204 (dec)
>> and can contain up to 7 32-bit words. This area is available to
>> programming in the z/Architecture Principles of Operation and
>> can thus safely be used by the firmware until the IPL has completed.
> 
> This content is set by QEMU/the ccw bios on every IPL, so we do not
> have to change anything for migration. Correct?
> 
Hm ... this is true for the netboot start address, but I am not sure
about the boot menu parameters added in a follow on patch. I'll comment
there...
[...]
-- 
Regards,
 Viktor Mihajlovski