Re: [Qemu-devel] [PATCH 2/3] geometry detection: use HDIO_GETGEO

[Alexander Graf]

On 02.05.2012, at 16:27, Christian Borntraeger <address@hidden> wrote:

> On 02/05/12 14:54, Alexander Graf wrote:
>> On 05/02/2012 01:38 PM, Paolo Bonzini wrote:
>>>> On 05/02/2012 01:26 PM, Paolo Bonzini wrote:
>>>>>> and everyone should be happy :). I would really like to have as
>>>>>> little #ifdef TARGET_S390 code in QEMU. And #ifdef __s390__ is
>>>>>> even worse,
>>>>>> as it means we won't be able to execise that code path on other
>>>>>> architectures.
>>>>> True, but how do you exercise that code path with DASD geometry
>>>>> on !__s390__?
>>>> If we make things a flag for the guessing code, it should work just
>>>> as well with image files, right?
>>> Only when they're not blank. :)  I was only thinking of #ifdef __s390__
>>> for the call to HDIO_GETGEO.
>> 
>> Well, if guessing is a function
>> 
>>  guess_size(disk_size, block_size)
>> 
>> then we would be able to do the same on an image file. Christian, would that 
>> work?
> 
> I think that the geometry values can not always be guessed correctly based on
> block_size and disk_size.
> 
> Stefan, can you clarify that?
> 
> If we cannot reliably guess the geometry based on blocksize and size, I still 
> think
> that we should use the host values, e.g. after checking that BIODASDINFO2 
> returns 
> successfully.

Yeah, but only if it's always possible to force a specific geometry through the 
command line - otherwise reproducability suffers.


Alex