Re: [Qemu-devel] [PATCH v14 0/2] virtio-crypto: virtio crypto device specification

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Mon, Dec 26, 2016 at 02:38:29AM +0000, Gonglei (Arei) wrote:
> Both Alex and Stefan mentioned that the process of create/close a session
> makes we have a least one full round-trip cost from guest to host to guest
> to be able to send any data for symmetric algorithms. It gets ourself into
> synchronization troubles in some scenarios like a web server handling lots
> of small requests whose algorithms and keys are different.
> 
> Because the virtio crypto specification has not been voted yet and v15 is on the way.
> I'd like to make some changes in order to support those scenarios better. That means
> we will support one-blob request (no sessions) as well for symmetric
> algorithms, including HASH, MAC services. The benefit is obvious for
> HASH service because it's usually a one-blob operation.
> 
> The main changes will be:
>  1) using the flag property of struct virtio_crypto_op_header to identify the
>     type of crypto request. Aka Is it a session-based or non-session request?
>     The flag is not used currently, so we can make use of it.
> 
>  2) extending virtio_crypto_*_para structures, for example, add the content of
>     struct virtio_crypto_cipher_session_para into struct virtio_crypto_cipher_para.
>     It's true that will increase the size of each crypto request after this change.
> 
> Does it make sense? Thanks!

That sounds good.  Hopefully many crypto API users only use a single
operation and can therefore benefit from this optimization.

Stefan

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