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

["Xia, Chenbo" <chenbo.xia@intel.com>]

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?

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