Re: [PATCH for-5.0] vpc: Don't round up already aligned BAT sizes

[Max Reitz]

On 03.04.20 14:04, Kevin Wolf wrote:
> Am 03.04.2020 um 10:55 hat Max Reitz geschrieben:
>> On 02.04.20 11:36, Kevin Wolf wrote:
>>> As reported on Launchpad, Azure apparently doesn't accept images for
>>> upload that are not both aligned to 1 MB blocks and have a BAT size that
>>> matches the image size exactly.
>>>
>>> As far as I can tell, there is no real reason why we create a BAT that
>>> is one entry longer than necessary for aligned image sizes, so change
>>> that.
>>>
>>> (Even though the condition is only mentioned as "should" in the spec and
>>> previous products accepted larger BATs - but we'll try to maintain
>>> compatibility with as many of Microsoft's ever-changing interpretations
>>> of the VHD spec as possible.)
>>
>> So as far as I can tell we still don’t ensure that the image is aligned
>> to 1 MB blocks?
>>
>> Well, as long as it’s at least possible for the user to create valid
>> images, that’s better.
> 
> Yes, we still allow other image sizes because Azure is not the only
> product using VHD images, but it is the only one (to my knowledge) that
> makes this requirement.
> 
> We're trying to stay compatible with at least three different Microsoft
> products (VirtualPC, HyperV, Azure) that all have their own
> interpretation of the spec and are inconsistent with each other.

OK, nice.  Thanks for the explanation!

Max

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