RE: [EXTERNAL] [PATCH v2 1/2] crypto/mlx5: optimize AES-GCM IPsec operation

[Akhil Goyal <gakhil@marvell.com>]

> Hi Akhil,
> 
> > -----Original Message-----
> > From: Akhil Goyal <gakhil@marvell.com>
> > Sent: Friday, June 14, 2024 2:49 PM
> > To: Suanming Mou <suanmingm@nvidia.com>; Matan Azrad
> > <matan@nvidia.com>
> > Cc: dev@dpdk.org
> > Subject: RE: [EXTERNAL] [PATCH v2 1/2] crypto/mlx5: optimize AES-GCM IPsec
> > operation
> >
> > > To optimize AES-GCM IPsec operation within crypto/mlx5, the DPDK API
> > > typically supplies AES_GCM AAD/Payload/Digest in separate locations,
> > > potentially disrupting their contiguous layout. In cases where the
> > > memory layout fails to meet hardware (HW) requirements, an UMR WQE is
> > > initiated ahead of the GCM's GGA WQE to establish a continuous
> > > AAD/Payload/Digest virtual memory space for the HW MMU.
> > >
> > > For IPsec scenarios, where the memory layout consistently adheres to
> > > the fixed order of AAD/IV/Payload/Digest, directly shrinking memory
> > > for AAD proves more efficient than preparing a UMR WQE. To address
> > > this, a new devarg "crypto_mode" with mode "ipsec_opt" is introduced
> > > in the commit, offering an optimization hint specifically for IPsec
> > > cases. When enabled, the PMD copies AAD directly before Payload in the
> > > enqueue_burst function instead of employing the UMR WQE. Subsequently,
> > > in the dequeue_burst function, the overridden IV before Payload is
> > > restored from the GGA WQE. It's crucial for users to avoid utilizing
> > > the input mbuf data during processing.
> >
> > This seems very specific to mlx5 and is not as per the expectations of cryptodev
> > APIs.
> >
> > It seems you are asking to alter the user application to accommodate this to
> > support IPsec.
> >
> > Cryptodev APIs are for generic crypto processing of data as defined in
> > rte_crypto_op.
> > With your proposed changes, it seems the behavior of the crypto APIs will be
> > different in case of mlx5 which I believe is not correct.
> >
> > Is it not possible for you to use rte_security IPsec path?
> >
> 
> Sorry I don't understand why that conflicts the API, IIUC crypto API only just
> defines the AAD/Payload/Digest in struct rte_crypto_sym_op, but not restrict the
> sequence, and AAD/Payload/Digest may come from difference memory space.
> Am I missing something here?

Yes you are correct that there is no restriction there.

> The input requirements from mlx5 HW is AAD/Payload/Digest sequence, if the
> input memory of AAD/Payload/Digest does not meet the requirements, PMD will
> try to combine the memory address space with UMR WQE as that commit does
> by software shrink.

And here, you are adding a restriction for IPsec case.
I believe you need a way to identify IPsec case with non-ipsec case in data path.
For that, instead of using a devarg(which is a specific case for mlx5),
you can use generic rte_security session with action type RTE_SECURITY_ACTION_TYPE_NONE.

You may also benefit from rte_ipsec library APIs and test framework,
for processing of protocol specific things which are specifically written
for RTE_SECURITY_ACTION_TYPE_NONE case.

> And the most important thing is that "ipsec_opt" is not mandatory, only if user
> have such case of layout and allows that optimization happens. Otherwise, the
> existing UMR WQE will still be the default behavior here.
> 
With this new devarg which application would you be using for testing?
I do not see a patch for application changes for the layout that you are mentioning.