Note, this is a cover letter - see important clarification below. Sorry, I missed adding the [PATCH 0/1] and [PATCH 1/1] to the email subject.
> -----Original Message----- > From: Trahe, Fiona > Sent: Thursday, November 17, 2016 5:33 PM > To: dev at dpdk.org > Cc: De Lara Guarch, Pablo <pablo.de.lara.guarch at intel.com>; Trahe, Fiona > <fiona.trahe at intel.com>; Griffin, John <john.griffin at intel.com>; > Jastrzebski, > MichalX K <michalx.k.jastrzebski at intel.com>; Kusztal, ArkadiuszX > <arkadiuszx.kusztal at intel.com> > Subject: [PATCH] crypto: remove unused digest-appended feature > > The cryptodev API had specified that if the digest address field was > left empty on an authentication operation, then the PMD would assume > the digest was appended to the source or destination data. > This case was not handled at all by most PMDs and incorrectly handled > by the QAT PMD. > As no bugs were raised, it is assumed to be not needed, so this patch > removes it, rather than add handling for the case on all PMDs. > The digest can still be appended to the data, but its > address must now be provided in the op. > > I've added this cover letter to pre-empt the question which will arise > in chained-mbuf case. > (Chained-mbuf support will be added in next few weeks for 17.02) > In a chained-mbuf case, if the digest is appended to the data, it could > in theory end up split across the last 2 mbufs. Using the digest address > field only works for the case where the digest is in a flat buffer. The > digest-appended feature would have provided one way of handling this, > pushing the responsibility down to the PMD to follow the chain to find > the digest address and handle it whether in 1 or 2 mbufs. > However, this is adding extra cycles on the data path in all PMDs > to handle a case which may not arise in many applications. > The alternative is to give the application the responsibility > to make sure the digest is in a flat buffer. > Specifically if an application knows cases of a digest spanning > buffers can arise, then it can check for this case and memcpy the partial > start of the digest from the second last buffer into the last buffer > so it's no longer split. > Does anyone see a problem with this? > > > Fiona Trahe (1): > crypto: remove unused digest-appended feature > > drivers/crypto/qat/qat_adf/qat_algs_build_desc.c | 2 ++ > drivers/crypto/qat/qat_crypto.c | 18 +----------------- > lib/librte_cryptodev/rte_crypto_sym.h | 10 +--------- > 3 files changed, 4 insertions(+), 26 deletions(-) > > -- > 2.5.0
