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

[Lluís Vilanova]

Lluís Vilanova writes:

> 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.

BTW, I think that having the softmmu-side of the backdoor inside ivshmem would
in fact be a simple change. I just want to make sure whether the reason to merge
both is about minimising code maintenance or rather thinking that it would make
more sense to have both as a single pack of functionalities.


Thanks,
  Lluis

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