From: Leon Romanovsky leonro@nvidia.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,
VFIO has always supported P2P mappings with itself. VFIO type 1 insecurely reads PFNs directly out of a VMA's PTEs and programs them into the IOMMU allowing any two VFIO devices to perform P2P to each other.
All existing VMMs use this capability to export P2P into a VM where the VM could setup any kind of DMA it likes. Projects like DPDK/SPDK are also known to make use of this, though less frequently.
As a first step to more properly integrating VFIO with the P2P subsystem unconditionally enable P2P support for VFIO PCI devices. The struct p2pdma_provider will act has a handle to the P2P subsystem to do things like DMA mapping.
While real PCI devices have to support P2P (they can't even tell if an IOVA is P2P or not) there may be fake PCI devices that may trigger some kind of catastrophic system failure. To date VFIO has never tripped up on such a case, but if one is discovered the plan is to add a PCI quirk and have pcim_p2pdma_init() fail. This will fully block the broken device throughout any users of the P2P subsystem in the kernel.
Thus P2P through DMABUF will follow the historical VFIO model and be unconditionally enabled by vfio-pci.
Signed-off-by: Leon Romanovsky leonro@nvidia.com --- drivers/vfio/pci/vfio_pci_core.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index ca9a95716a85..142b84b3f225 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -28,6 +28,7 @@ #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 @@ -2081,6 +2082,7 @@ 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 ret;
vdev->pdev = to_pci_dev(core_vdev->dev); vdev->irq_type = VFIO_PCI_NUM_IRQS; @@ -2090,6 +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); + ret = pcim_p2pdma_init(vdev->pdev); + if (ret && ret != -EOPNOTSUPP) + return ret; init_rwsem(&vdev->memory_lock); xa_init(&vdev->ctx);