Re: [Qemu-devel] [PATCH v2 4/5] backdoor: [softmmu] Add QEMU-side proxy to "libbackdoor.a"

[Lluís Vilanova]

Anthony Liguori writes:

> I really worry about us introducing so many of these one-off paravirtual 
> devices.
> I would much prefer that you look at doing this as an extension to the ivshmem
> device as it already has this sort of scope.  You should be able to do this by
> just extending the size of bar 1 and using a well known guest id.

I did in fact look at ivshmem some time ago, and it's true that both use the
same mechanisms; but each device has a completely different purpose. To me it
just seems that extending the control BAR in ivshmem to call the user-provided
backdoor callbacks is just conflating two completely separate devices into a
single one. Besides, I think that the qemu-side of the backdoor is simple enough
to avoid being a maintenance burden.

Another question would be to join both so that the backdoor can be used to
orchestrate operations between multiple VMs through ivshmem's server, but I
really have no time to look into that and don't even know whether it would then
make sense to join both devices.


Thanks,
  Lluis

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