[Qemu-devel] Re: [PATCH 0/2] fix virtio_blk serial pci config breakage

[Anthony Liguori]

Rusty Russell wrote:
> On Tue, 29 Sep 2009 11:25:20 pm Anthony Liguori wrote:
>   
> > 2) Passing an ATA identity page is goofy.  We should just pass the 
> > serial number and let Linux generate the identity page.  Just because 
> > Linux requires this as it's user space interface, that doesn't mean that 
> > other guests will (like Windows).  Instead of exposing an opaque blob, 
> > we should expose the information we need in a structured way.
> >     
>
> I think John did this on my prompting, because it already existed as a
> defined ABI.  If someone is going to make stuff up, isn't it better that
> kvm does it (some of those fields might have useful values?) than linux?
>   

We should expose Linux ABI quirks in the virtio ABI.  Down the road, 
someone may decide that there's a better way to expose things like S/N 
down to userspace and then in our drivers we would have to parse the ATA 
identity page in order to figure out the S/N to expose that properly 
through the new interface.  Moreover, there's probably an OS out there 
that we already have to do that for.

That's a pretty ugly thing to have to do.

> (I don't care: my patches stick with the current scheme, but changing is
> fairly easy, but needs to be decided before commit).
>   

Everything is tremendously simplified if we just expose the S/N in the 
ABI since we can avoid solving the config size limitation.  I'm a big 
fan of deferring difficult problems when there's an immediate easy 
solution :-)

> Thanks,
> Rusty,
>