Re: [dpdk-dev] [PATCH] doc: announce change in vfio dma mapping

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Ferruh,

> -----Original Message-----
> From: Yigit, Ferruh <ferruh.yigit@intel.com>
> Sent: Wednesday, September 1, 2021 12:01 AM
> To: Ding, Xuan <xuan.ding@intel.com>; dev@dpdk.org; Burakov, Anatoly
> <anatoly.burakov@intel.com>
> Cc: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>; Hu,
> Jiayu <jiayu.hu@intel.com>; Richardson, Bruce <bruce.richardson@intel.com>
> Subject: Re: [PATCH] doc: announce change in vfio dma mapping
> 
> On 8/31/2021 2:10 PM, Xuan Ding wrote:
> > Currently, the VFIO subsystem will compact adjacent DMA regions for the
> > purposes of saving space in the internal list of mappings. This has a
> > side effect of compacting two separate mappings that just happen to be
> > adjacent in memory. Since VFIO implementation on IA platforms also does
> > not allow partial unmapping of memory mapped for DMA, the current
> DPDK
> > VFIO implementation will prevent unmapping of accidentally adjacent
> > maps even though it could have been unmapped [1].
> >
> > The proper fix for this issue is to change the VFIO DMA mapping API to
> > also include page size, and always map memory page-by-page.
> >
> > [1] https://mails.dpdk.org/archives/dev/2021-July/213493.html
> >
> > Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> > ---
> >  doc/guides/rel_notes/deprecation.rst | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/doc/guides/rel_notes/deprecation.rst
> b/doc/guides/rel_notes/deprecation.rst
> > index 76a4abfd6b..1234420caf 100644
> > --- a/doc/guides/rel_notes/deprecation.rst
> > +++ b/doc/guides/rel_notes/deprecation.rst
> > @@ -287,3 +287,6 @@ Deprecation Notices
> >    reserved bytes to 2 (from 3), and use 1 byte to indicate warnings and
> other
> >    information from the crypto/security operation. This field will be used to
> >    communicate events such as soft expiry with IPsec in lookaside mode.
> > +
> > +* vfio: the functions `rte_vfio_container_dma_map` will be amended to
> > +  include page size. This change is targeted for DPDK 22.02.
> >
> 
> Is this means adding a new parameter to API?
> If so this is an ABI/API break and we can't do this change in the 22.02.

Our original plan is add a new parameter in order not to use a new function name, so you mean, any changes to the API can only be done in the LTS version?
If so, we can only add a new API and retire the old one in 22.11.

Thanks for you classification.