[PATCH 0/3] block: Enable proper MMIO memory handling for P2P DMA

Leon Romanovsky
2025-10-17T05:32:10Z

Changelog:
v1:
* 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 (3):
blk-mq-dma: migrate to dma_map_phys instead of map_page
nvme-pci: unmap MMIO pages with appropriate interface
block-dma: properly take MMIO path

block/blk-mq-dma.c | 12 +++++++++---
drivers/nvme/host/pci.c | 18 +++++++++++++-----
include/linux/bio-integrity.h | 1 +
include/linux/blk-integrity.h | 3 ++-
include/linux/blk-mq-dma.h | 14 +++++++++++---
include/linux/blk_types.h | 2 ++
6 files changed, 38 insertions(+), 12 deletions(-)
---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251016-block-with-mmio-02acf4285427

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