[PATCH v3 0/2] block: Enable proper MMIO memory handling for P2P DMA

Leon Romanovsky
2025-10-27T07:30:50Z

Changelog:
v3:
* Encoded p2p map type in IOD flags instead of DMA attributes.
* Removed REQ_P2PDMA flag from block layer.
* Simplified map_phys conversion patch.
v2: https://lore.kernel.org/all/20251020-block-with-mmio-v2-0-147e9f93d8d4@nvidia.com/
* Added Chirstoph's Reviewed-by tag for first patch.
* Squashed patches
* Stored DMA MMIO attribute in NVMe IOD flags variable instead of block layer.
v1: https://patch.msgid.link/20251017-block-with-mmio-v1-0-3f486904db5e@nvidia.com
* Reordered patches.
* Dropped patch which tried to unify unmap flow.
* Set MMIO flag separately for data and integrity payloads.
v0: https://lore.kernel.org/all/cover.1760369219.git.leon@kernel.org/

----------------------------------------------------------------------

This patch series improves block layer and NVMe driver support for MMIO
memory regions, particularly for peer-to-peer (P2P) DMA transfers that
go through the host bridge.

The series addresses a critical gap where P2P transfers through the host
bridge (PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) were not properly marked as
MMIO memory, leading to potential issues with:

- Inappropriate CPU cache synchronization operations on MMIO regions
- Incorrect DMA mapping/unmapping that doesn't respect MMIO semantics
- Missing IOMMU configuration for MMIO memory handling

This work is extracted from the larger DMA physical API improvement
series [1] and focuses specifically on block layer and NVMe requirements
for MMIO memory support.

Thanks

[1] https://lore.kernel.org/all/cover.1757423202.git.leonro@nvidia.com/

Leon Romanovsky (2):
nvme-pci: migrate to dma_map_phys instead of map_page
block-dma: properly take MMIO path

block/blk-mq-dma.c | 19 ++++++----
drivers/nvme/host/pci.c | 86 +++++++++++++++++++++++++++++++++++--------
include/linux/bio-integrity.h | 1 -
include/linux/blk-integrity.h | 14 -------
include/linux/blk-mq-dma.h | 28 +++++++-------
include/linux/blk_types.h | 2 -
6 files changed, 95 insertions(+), 55 deletions(-)
---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251016-block-with-mmio-02acf4285427

Best regards,
--
Leon Romanovsky <leonro@nvidia.com>