[PATCH v2 3/5] IB/core: P2P DMA for device private pages

[Yonatan Maman]

From: Yonatan Maman <Ymaman at Nvidia.com>

Add Peer-to-Peer (P2P) DMA request for hmm_range_fault calling,
utilizing capabilities introduced in mm/hmm. By setting
range.default_flags to HMM_PFN_REQ_FAULT | HMM_PFN_REQ_TRY_P2P, HMM
attempts to initiate P2P DMA connections for device private pages
(instead of page fault handling).

This enhancement utilizes P2P DMA to reduce performance overhead
during data migration between devices (e.g., GPU) and system memory,
providing performance benefits for GPU-centric applications that
utilize RDMA and device private pages.

Signed-off-by: Yonatan Maman <Ymaman at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom at Nvidia.com>
---
 drivers/infiniband/core/umem_odp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index b1c44ec1a3f3..7ba80ed4977c 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -362,6 +362,10 @@ int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,
 			range.default_flags |= HMM_PFN_REQ_WRITE;
 	}
 
+	if (access_mask & HMM_PFN_ALLOW_P2P)
+		range.default_flags |= HMM_PFN_ALLOW_P2P;
+
+	range.pfn_flags_mask = HMM_PFN_ALLOW_P2P;
 	range.hmm_pfns = &(umem_odp->map.pfn_list[pfn_start_idx]);
 	timeout = jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
 
-- 
2.34.1