Re: [Qemu-devel] [Qemu-trivial] [PATCH] vmdk: Fix cylinders number during convert

[Markus Armbruster]

Michael Tokarev <address@hidden> writes:

> On 10/22/2014 05:25 PM, Arthur Gautier wrote:
>> We can not rely on int cast to get a correct number of cylinders. The
>> cylinders information was wrong in 49.9999% of cases.
>> 
>> This ensures the cylinders always gets the ceiling value.
>
> Good thing, especially the good probability :), and also a good patch
> which comes with a test.
>
> But I wonder if anything can break this way?  Migration, windows guest
> being unable to find its partitions, something else?
>
> And more.  What-if our drive size in cylinders will be larger than
> the size in bytes?  The proposed div_round_up() will increase number
> of cylinders, so size in CHS will be larger than size in bytes.  Maybe
> there was a reason why originally the size in cylinders was calculated
> by truncating extra fractional part?  What-if guest will try to access
> the very last CHS which is incomplete?

Too many questions for -trivial, copying VMDK maintainers.