Re: [Qemu-devel] [PATCH v8 1/2] virtio-crypto: Add virtio crypto device specification

[Alexander Graf <agraf@suse.de>]

On 09/04/2016 05:47 PM, Ola Liljedahl wrote:
>
> On 02/09/2016, 16:05, "Alexander Graf" <agraf@suse.de> wrote:
>
>>>> There is a big problem that the control handle logic is synchronization,
>>>> but the data queue
>>>> handling logic is asynchronization. We can't combine them into one
>>>> queue.
>>>> It will decrease the performance because you need indentify each packet
>>>> if we do this forcedly.
>>> Are you saying that control and data operations are handled by separate
>>> "blocks²?
>>> If you combined control and data queues, there would have to be a (SW)
>>> demultiplexer
>>> that would add overhead (and potentially decrease throughout) especially
>>> for the data
>>> operations?
>> Uh, the multiplexer is as simple as a switch() statement on the opcode,
>> no?
> You are assuming the backend will (always) be implemented in software.

If you implement it in something that is not software, multiplexing
suddenly becomes a lot harder. What if you want to run 20 VMs on a
single host? Would you spawn SR-IOV devices with separate control queues
each? Or would you trap the control queue into the host and let the
guest freely access data queues which then means one guest could
interfere with another guest's data?

If you manage to give each queue its own stream ID, you could just pass
as many real hardware queues as you like into guests, no?


Alex