linux-kernel - [PATCH v1 3/4] IB/core: P2P DMA for device private pages

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Message-ID: <20241015152348.3055360-4-ymaman@nvidia.com>
Date: Tue, 15 Oct 2024 18:23:47 +0300
From: Yonatan Maman <ymaman@...dia.com>
To: <nouveau@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<linux-rdma@...r.kernel.org>, <linux-mm@...ck.org>, <herbst@...hat.com>,
	<lyude@...hat.com>, <dakr@...hat.com>, <airlied@...il.com>,
	<simona@...ll.ch>, <jgg@...pe.ca>, <leon@...nel.org>, <jglisse@...hat.com>,
	<akpm@...ux-foundation.org>, <dri-devel@...ts.freedesktop.org>,
	<apopple@...dia.com>, <bskeggs@...dia.com>
CC: Yonatan Maman <Ymaman@...dia.com>, Gal Shalom <GalShalom@...dia.com>
Subject: [PATCH v1 3/4] IB/core: P2P DMA for device private pages

From: Yonatan Maman <Ymaman@...dia.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@...dia.com>
Reviewed-by: Gal Shalom <GalShalom@...dia.com>
---
 drivers/infiniband/core/umem_odp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index e9fa22d31c23..1f6498d26df4 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -381,7 +381,7 @@ int ib_umem_odp_map_dma_and_lock(struct ib_umem_odp *umem_odp, u64 user_virt,
 	pfn_start_idx = (range.start - ib_umem_start(umem_odp)) >> PAGE_SHIFT;
 	num_pfns = (range.end - range.start) >> PAGE_SHIFT;
 	if (fault) {
-		range.default_flags = HMM_PFN_REQ_FAULT;
+		range.default_flags = HMM_PFN_REQ_FAULT | HMM_PFN_REQ_ALLOW_P2P;
 
 		if (access_mask & ODP_WRITE_ALLOWED_BIT)
 			range.default_flags |= HMM_PFN_REQ_WRITE;
-- 
2.34.1