RE: [PATCH 1/2] doc: announce region based device mapping support

[Sunil Kumar Kori <skori@marvell.com>]

Regards
Sunil Kumar Kori

> -----Original Message-----
> From: Xia, Chenbo <chenbo.xia@intel.com>
> Sent: Wednesday, July 13, 2022 12:58 PM
> To: Sunil Kumar Kori <skori@marvell.com>; Ray Kinsella <mdr@ashroe.eu>
> Cc: dev@dpdk.org; David Marchand <david.marchand@redhat.com>
> Subject: [EXT] RE: [PATCH 1/2] doc: announce region based device mapping
> support
> 
> External Email
> 
> ----------------------------------------------------------------------
> Hi Sunil,
> 
> > -----Original Message-----
> > From: Sunil Kumar Kori <skori@marvell.com>
> > Sent: Wednesday, July 13, 2022 3:04 PM
> > To: Xia, Chenbo <chenbo.xia@intel.com>; Ray Kinsella <mdr@ashroe.eu>
> > Cc: dev@dpdk.org
> > Subject: RE: [PATCH 1/2] doc: announce region based device mapping
> > support
> >
> > Hi Chenbo,
> >
> > There are pci devices which has huge BAR memory but might not be used
> > completely.
> > Like PCIe device DDR memory is exposed over BAR with 32Gb or so.
> > So in that case user might have a requirement to mmap only areas of
> > its interest.
> > Also avoid wasting of extra memory for each pages when kernel mmaps it.
> 
> This problem statement makes sense to me. About the solution, pls check
> below.
> 
> >
> > Yes, it is similar to sparse mmap in vfio but I didn't find any
> > support in DPDK for sparse mmap.
> > So I picked this approach but in either case, ABI change notification
> > is needed, Right?
> 
> For ABI, David & I already mentioned in another email that your notice is not
> needed anymore.
> 
> What if you send the patchset to support sparse mmap in DPDK, to me, that
> seems more generic. Could sparse mmap solve your problem?

I will look into sparse mmap and analyze its feasibility to solve my problem.
Will update accordingly. 

Thanks Chenbo and David.
> 
> Thanks,
> Chenbo
> 
> >
> > Regards
> > Sunil Kumar Kori
> >
> > > -----Original Message-----
> > > From: Xia, Chenbo <chenbo.xia@intel.com>
> > > Sent: Thursday, July 7, 2022 6:09 PM
> > > To: Sunil Kumar Kori <skori@marvell.com>; Ray Kinsella
> > > <mdr@ashroe.eu>
> > > Cc: dev@dpdk.org
> > > Subject: [EXT] RE: [PATCH 1/2] doc: announce region based device
> > > mapping support
> > >
> > > External Email
> > >
> > > --------------------------------------------------------------------
> > > --
> > > Hi Sunil,
> > >
> > > > -----Original Message-----
> > > > From: skori@marvell.com <skori@marvell.com>
> > > > Sent: Tuesday, June 28, 2022 9:54 PM
> > > > To: Ray Kinsella <mdr@ashroe.eu>
> > > > Cc: dev@dpdk.org; Sunil Kumar Kori <skori@marvell.com>
> > > > Subject: [PATCH 1/2] doc: announce region based device mapping
> > > > support
> > > >
> > > > From: Sunil Kumar Kori <skori@marvell.com>
> > > >
> > > > Adding region based device mapping support, which enables pci
> > > > device to map only required memory region instead of mapping full
> BAR.
> > >
> > > Why there will be such requirement to mmap only part of BAR when the
> > > BAR can be fully mmapped. I thought you want to enable something
> > > like sparse mmap feature in VFIO, but seems it's a feature that let
> > > driver ask for
> > specific
> > > mmap option. Could you explain the use case here?
> > >
> > > Thanks,
> > > Chenbo
> > >
> > > >
> > > > Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
> > > > ---
> > > >  doc/guides/rel_notes/deprecation.rst | 13 +++++++++++++
> > > >  1 file changed, 13 insertions(+)
> > > >
> > > > diff --git a/doc/guides/rel_notes/deprecation.rst
> > > > b/doc/guides/rel_notes/deprecation.rst
> > > > index 4e5b23c53d..8800a3eb41 100644
> > > > --- a/doc/guides/rel_notes/deprecation.rst
> > > > +++ b/doc/guides/rel_notes/deprecation.rst
> > > > @@ -125,3 +125,16 @@ Deprecation Notices
> > > >    applications should be updated to use the ``dmadev`` library
> > instead,
> > > >    with the underlying HW-functionality being provided by the
> > > > ``ioat``
> > or
> > > >    ``idxd`` dma drivers
> > > > +
> > > > +* pci: Update ``rte_pci_device`` and ``rte_pci_driver`` to add
> > > > +region
> > > > based
> > > > +  memory mapping support. There could be a requirement to mmap
> > > > + specific
> > > > memory
> > > > +  region only. Using this mechanism, pci device can be mapped for
> > > > + a given BAR at a given offset of given size.
> > > > +
> > > > +  ``rte_pci_device`` will be added with following field
> > > > + ``regions[PCI_MAX_RESOURCE][PCI_MAX_REGION_PER_RESOURCE];``.
> > > This
> > > > + field
> > > > will
> > > > +  specify the regions which are mapped for a given BAR.
> > > > +
> > > > +  ``rte_pci_driver`` will be added with ``rte_pci_region_map
> > > > + *regions``
> > > > and
> > > > +  ``valid_bars[PCI_MAX_RESOURCE]``. Using these fields, driver
> > > > + can
> > > > propagate
> > > > +  its region information which are required to be mmap.
> > > > --
> > > > 2.25.1