linux-kernel - [PATCH 08/10] vfio/pci: Enable peer-to-peer DMA transactions by default

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Message-ID: <a55d0868fbf7e9000ed46c6d45928e5b9a5cae1f.1753274085.git.leonro@nvidia.com>
Date: Wed, 23 Jul 2025 16:00:09 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: Leon Romanovsky <leonro@...dia.com>,
	Christoph Hellwig <hch@....de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org,
	iommu@...ts.linux.dev,
	Jens Axboe <axboe@...nel.dk>,
	Jérôme Glisse <jglisse@...hat.com>,
	Joerg Roedel <joro@...tes.org>,
	kvm@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	linux-mm@...ck.org,
	linux-pci@...r.kernel.org,
	Logan Gunthorpe <logang@...tatee.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Will Deacon <will@...nel.org>
Subject: [PATCH 08/10] vfio/pci: Enable peer-to-peer DMA transactions by default

From: Leon Romanovsky <leonro@...dia.com>

Make sure that all VFIO PCI devices have peer-to-peer capabilities
enables, so we would be able to export their MMIO memory through DMABUF,

Signed-off-by: Leon Romanovsky <leonro@...dia.com>
---
 drivers/vfio/pci/vfio_pci_core.c | 4 ++++
 include/linux/vfio_pci_core.h    | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 6328c3a05bcdd..1e675daab5753 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -29,6 +29,7 @@
 #include <linux/nospec.h>
 #include <linux/sched/mm.h>
 #include <linux/iommufd.h>
+#include <linux/pci-p2pdma.h>
 #if IS_ENABLED(CONFIG_EEH)
 #include <asm/eeh.h>
 #endif
@@ -2091,6 +2092,9 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev)
 	INIT_LIST_HEAD(&vdev->dummy_resources_list);
 	INIT_LIST_HEAD(&vdev->ioeventfds_list);
 	INIT_LIST_HEAD(&vdev->sriov_pfs_item);
+	vdev->provider = pci_p2pdma_enable(vdev->pdev);
+	if (IS_ERR(vdev->provider))
+		return PTR_ERR(vdev->provider);
 	init_rwsem(&vdev->memory_lock);
 	xa_init(&vdev->ctx);
 
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index fbb472dd99b36..b017fae251811 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -94,6 +94,7 @@ struct vfio_pci_core_device {
 	struct vfio_pci_core_device	*sriov_pf_core_dev;
 	struct notifier_block	nb;
 	struct rw_semaphore	memory_lock;
+	struct p2pdma_provider  *provider;
 };
 
 /* Will be exported for vfio pci drivers usage */
-- 
2.50.1