[dpdk-dev] [PATCH] doc: flow rule removal on port stop
Gregory Etelson
getelson at nvidia.com
Wed Nov 18 09:59:53 CET 2020
Hello Andrew,
> On 11/17/20 10:18 PM, Gregory Etelson wrote:
> > There is a discrepancy between RTE ETHDEV API and flow rules guide
> > regarding flow rules maintenance after port stop. RTE ETHDEV API in
> > librte_ethdev.h declares that flow rules will not be stored in PMD
> > after port stop:
> > >>>>> Quite start
> > Please note that some configuration is not stored between calls to
> > rte_eth_dev_stop()/rte_eth_dev_start(). The following configuration
> > will be retained:
> >
> > - MTU
> > - flow control settings
> > - receive mode configuration (promiscuous mode, all-multicast mode,
> > hardware checksum mode, RSS/VMDQ settings etc.)
> > - VLAN filtering configuration
> > - default MAC address
> > - MAC addresses supplied to MAC address array
> > - flow director filtering mode (but not filtering rules)
> > - NIC queue statistics mappings
> > <<<< Quote end
> >
> > PMD cannot always correctly restore flow rules after port stop / port
> > start because application may alter port configuration after port stop
> > without PMD knowledge about undergoing changes. Consider the
> > following scenario:
> > application configures 2 queues 0 and 1 and creates a flow rule with
> > 'queue index 1' action. After that application stops the port and
> > removes queue 1.
> > Although PMD can implement flow rule shadow copy to be used for
> > restore after port start, attempt to restore flow rule from shadow
> > will fail in example above and PMD could not notify application about
> > that failure. As the result, flow rules map in HW will differ from
> > what application expects. In addition, flow rules shadow copy used
> > for port start restore consumes considerable amount of system memory,
> > especially in systems with millions of flow rules.
> >
> > Signed-off-by: Gregory Etelson <getelson at nvidia.com>
> > Acked-by: Ori Kam <orika at nvidia.com>
> > ---
> > doc/guides/prog_guide/rte_flow.rst | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/doc/guides/prog_guide/rte_flow.rst
> > b/doc/guides/prog_guide/rte_flow.rst
> > index 944e8242d6..dfe5a40f8e 100644
> > --- a/doc/guides/prog_guide/rte_flow.rst
> > +++ b/doc/guides/prog_guide/rte_flow.rst
> > @@ -3055,10 +3055,9 @@ Caveats
> > temporarily replacing the burst function pointers), an appropriate
> error
> > code must be returned (``EBUSY``).
> >
> > -- PMDs, not applications, are responsible for maintaining flow rules
> > +- Applications, not PMDs, are responsible for maintaining flow rules
> > configuration when stopping and restarting a port or performing
> > other
> > - actions which may affect them. They can only be destroyed
> > explicitly by
> > - applications.
> > + actions which may affect them.
> >
> > For devices exposing multiple ports sharing global settings affected
> by flow
> > rules:
> >
>
> Re-reading it, it still looks vague. What happens on:
> - port stop without removal of flow rule before
> - port close without removal of flow rules before
> - port reset (which could be stop/start, e.g. to recover from error
> condition)
PMD should remove all flows related to hardware resource that was invalidated.
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