linux-kernel - [PATCH v4 08/10] vfio/pci: Enable peer-to-peer DMA transactions by default

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Message-ID: <ac8c6ccd792e79f9424217d4bca23edd249916ca.1759070796.git.leon@kernel.org>
Date: Sun, 28 Sep 2025 17:50:18 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: Leon Romanovsky <leonro@...dia.com>,
	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>,
	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 v4 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 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 7dcf5439dedc..608af135308e 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -28,6 +28,9 @@
 #include <linux/nospec.h>
 #include <linux/sched/mm.h>
 #include <linux/iommufd.h>
+#ifdef CONFIG_VFIO_PCI_DMABUF
+#include <linux/pci-p2pdma.h>
+#endif
 #if IS_ENABLED(CONFIG_EEH)
 #include <asm/eeh.h>
 #endif
@@ -2085,6 +2088,7 @@ int vfio_pci_core_init_dev(struct vfio_device *core_vdev)
 {
 	struct vfio_pci_core_device *vdev =
 		container_of(core_vdev, struct vfio_pci_core_device, vdev);
+	int __maybe_unused ret;
 
 	vdev->pdev = to_pci_dev(core_vdev->dev);
 	vdev->irq_type = VFIO_PCI_NUM_IRQS;
@@ -2094,6 +2098,11 @@ 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);
+#ifdef CONFIG_VFIO_PCI_DMABUF
+	ret = pcim_p2pdma_init(vdev->pdev);
+	if (ret)
+		return ret;
+#endif
 	init_rwsem(&vdev->memory_lock);
 	xa_init(&vdev->ctx);
 
-- 
2.51.0