Re: [Qemu-devel] [virtio-dev] Re: [PATCH v15 0/2] virtio-crypto: virtio crypto device specification

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jan 13, 2017 at 02:54:29AM +0000, Gonglei (Arei) wrote:
> 
> > 
> > On Thu, Jan 12, 2017 at 12:26:24PM +0000, Gonglei (Arei) wrote:
> > > Hi,
> > >
> > >
> > > >
> > > > On 01/04/2017 11:10 AM, Gonglei (Arei) wrote:
> > > > > Hi all,
> > > > >
> > > > > I attach the diff files between v14 and v15 for better review.
> > > > >
> > > > Hi,
> > > >
> > > > only had a quick look. Will try to come back to this later.
> > > >
> > > That's cool.
> > >
> > > > > diff --git a/virtio-crypto.tex b/virtio-crypto.tex
> > > > > index 9f7faf0..884ee95 100644
> > > > > --- a/virtio-crypto.tex
> > > > > +++ b/virtio-crypto.tex
> > > > > @@ -2,8 +2,8 @@
> > > > >
> > > > >  The virtio crypto device is a virtual cryptography device as well as a kind
> > of
> > > > >  virtual hardware accelerator for virtual machines. The encryption and
> > > > > -decryption requests are placed in the data queue and are ultimately
> > handled
> > > > by the
> > > > > -backend crypto accelerators. The second queue is the control queue used
> > to
> > > > create
> > > > > +decryption requests are placed in any of the data active queues and are
> > > > ultimately handled by the
> > > > s/data active/active data/
> > > > > +backend crypto accelerators. The second kind of queue is the control
> > queue
> > > > used to create
> > > > >  or destroy sessions for symmetric algorithms and will control some
> > > > advanced
> > > > >  features in the future. The virtio crypto device provides the following
> > crypto
> > > > >  services: CIPHER, MAC, HASH, and AEAD.
> > > >
> > > > [..]
> > > >
> > > > > ===============The below diff shows the changes of add non-session
> > mode
> > > > support:
> > > > >
> > > > > diff --git a/virtio-crypto.tex b/virtio-crypto.tex
> > > > > index 884ee95..44819f9 100644
> > > > > --- a/virtio-crypto.tex
> > > > > +++ b/virtio-crypto.tex
> > > > > @@ -26,7 +26,10 @@ N is set by \field{max_dataqueues}.
> > > > >
> > > > >  \subsection{Feature bits}\label{sec:Device Types / Crypto Device /
> > Feature
> > > > bits}
> > > > >
> > > > > -None currently defined.
> > > > > +VIRTIO_CRYPTO_F_CIPHER_SESSION_MODE (1) Session mode is
> > available
> > > > for CIPHER service.
> > > > > +VIRTIO_CRYPTO_F_HASH_SESSION_MODE (2) Session mode is available
> > for
> > > > HASH service.
> > > > > +VIRTIO_CRYPTO_F_MAC_SESSION_MODE (3) Session mode is available
> > for
> > > > MAC service.
> > > > > +VIRTIO_CRYPTO_F_AEAD_SESSION_MODE (4) Session mode is available
> > for
> > > > AEAD service.
> > > > >
> > > > >  \subsection{Device configuration layout}\label{sec:Device Types /
> > Crypto
> > > > Device / Device configuration layout}
> > > > >
> > > > > @@ -208,6 +211,9 @@ Operation parameters are algorithm-specific
> > > > parameters, output data is the
> > > > >  data that should be utilized in operations, and input data is equal to
> > > > >  "operation result + result data".
> > > > >
> > > > > +The device can support both session mode (See \ref{sec:Device Types /
> > > > Crypto Device / Device Operation / Control Virtqueue / Session operation})
> > and
> > > > non-session mode, for example,
> > > > > +As VIRTIO_CRYPTO_F_CIPHER_SESSION feature bit is negotiated, the
> > driver
> > > > can use session mode for CIPHER service, otherwise it can only use
> > non-session
> > > > mode.
> > > > > +
> > > >
> > > > As far as I understand you are adding non-session mode to the mix but
> > > > providing feature bits for session mode. Would this render the the current
> > > > implementation non-compliant?
> > > >
> > > You are right, shall we use feature bits for non-session mode for compliancy?
> > > Or because the spec is on the fly, and some structures in the virtio_crypto.h
> > need to
> > > be modified, can we keep the compliancy completely?
> > >
> > > Thanks,
> > > -Gonglei
> > 
> > Since there's a linux driver upstream you must at least
> > keep compatibility with that.
> > 
> Sure. We use feature bits for non-session mode then.
> For structures modification, do we need to do some specific
> actions for compatibility?  Take CIPHER service as an example:
> 
> The present structure:
> 
> struct virtio_crypto_cipher_para {
>     /*
>      * Byte Length of valid IV/Counter data pointed to by the below iv data.
>      *
>      * For block ciphers in CBC or F8 mode, or for Kasumi in F8 mode, or for
>      *   SNOW3G in UEA2 mode, this is the length of the IV (which
>      *   must be the same as the block length of the cipher).
>      * For block ciphers in CTR mode, this is the length of the counter
>      *   (which must be the same as the block length of the cipher).
>      */
>     le32 iv_len;
>     /* length of source data */
>     le32 src_data_len;
>     /* length of destination data */
>     le32 dst_data_len;
> };
> 
> The future structure if supporting non-session based operations:
> 
> struct virtio_crypto_cipher_para {
>     struct {
>         /* See VIRTIO_CRYPTO_CIPHER* above */
>         le32 algo;
>         /* length of key */
>         le32 keylen;
> 
>         /* See VIRTIO_CRYPTO_OP_* above */
>         le32 op;
>     } sess_para;
> 
>     /*
>      * Byte Length of valid IV/Counter data pointed to by the below iv data.
>      *
>      * For block ciphers in CBC or F8 mode, or for Kasumi in F8 mode, or for
>      *   SNOW3G in UEA2 mode, this is the length of the IV (which
>      *   must be the same as the block length of the cipher).
>      * For block ciphers in CTR mode, this is the length of the counter
>      *   (which must be the same as the block length of the cipher).
>      */
>     le32 iv_len;
>     /* length of source data */
>     le32 src_data_len;
>     /* length of destination data */
>     le32 dst_data_len;
> };
> 
> Thanks,
> -Gonglei

So you will have to maintain both structures for when non-session based
feature is and aren't present. You will have to give them different
names, too.

-- 
MST