io_uring and crypto

[David Howells <dhowells@redhat.com>]

Hi Jens,

I was wondering if it might be possible to adapt io_uring to make crypto
requests as io_uring primitives rather than just having io_uring call sendmsg
and recvmsg on an AF_ALG socket.

The reason I think this might make sense is that for the certain crypto ops we
need to pass two buffers, one input and one output (encrypt, decrypt, sign) or
two input (verify) and this could directly translate to an async crypto
request.

Or possibly we should have a sendrecv socket call (RPC sort of thing) and have
io_uring drive that.

The tricky bit is that it would require two buffers and io_uring seems geared
around one.

David