[dpdk-dev] [PATCH] doc: announce change in dma mapping/unmapping

[Xuan Ding]

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 at 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..272ffa993e 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` and `rte_vfio_container_dma_unmap`
+  will be amended to include page size. This change is targeted for DPDK 21.11.
-- 
2.17.1