L;w

-----Original Message-----
From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Gaëtan Rivet
Sent: Thursday, June 01, 2017 5:38 PM
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v4 08/12] net/failsafe: support offload
capabilities

On Wed, May 31, 2017 at 08:23:09AM -0700, Stephen Hemminger wrote:

quoted

On Mon, 29 May 2017 15:42:20 +0200
Gaetan Rivet [off-list ref] wrote:

quoted

Signed-off-by: Gaetan Rivet <redacted>
Acked-by: Olga Shern <redacted>
---
 doc/guides/nics/features/failsafe.ini |   6 ++
 drivers/net/failsafe/failsafe_ops.c   | 131

+++++++++++++++++++++++++++++++++-

quoted

quoted

 2 files changed, 135 insertions(+), 2 deletions(-)

Once again what about case of dumb synthetic NIC combined with SR-IOV

VF?

quoted

The VF has offloads the virtual NIC does not.

The rules for capabilities are a little complicated.
In the case both VF and the virtual NIC are present at launch, then the logical
AND is done both their capabilities sets.
If one has additional capabilities that the user is requesting, and the fail-safe
recognize them (currently, all RX offloads, as TX offloads were not yet
expressed by flags), and this capability is not supported by one slave, then
this offload is disabled in the configuration.

quoted

What about late plugin. how do you program the offloads of the later
arriving VF device.

If the VF is not present at launch, then the fail-safe reads only the set of
capabilities from the fallback device. It does not have to do any AND-ing of
the flags.

The consequence is that upon plugin of the VF, the latter has to respect the
current running configuration. Probing will actually fail if some capability is not
supported (depending on PMDs), and the running configuration is not
updated as it is considered "live".

There are only two solutions to this, either:

* Complicate a lot the fail-safe design and the rules applied in
  the decision made on NIC configuration. The user then has bad
  surprises upon seeing that his performance have been degraded
  for arcane reasons.

* Emulate in software the offloads and try to advertize as many as
  possible. This is done for example in the TAP PMD for some flags,
  allowing those offloads to be used with hardware NICs.
  The user then has a clear view of the available offloads by comparing
  both sets of capabilities.

--
Gaëtan Rivet
6WIND