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

[Kevin Wolf]

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.

Kevin

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