[RFC PATCH 3/5] vfio/pci: Block mmap & dmabuf export for ZONE_DEVICE-registered BARs

[Pranjal Shrivastava <praan@google.com>]

Update vfio_pci_core_mmap() &  vfio_pci_core_feature_dma_buf() to
enforce mutual exclusivity with ZONE_DEVICE P2P registration.

If a BAR has been registered for native P2P (via
VFIO_DEVICE_FEATURE_P2P_REGISTER), subsequent requests to mmap the BAR
or export it as a DMABUF are rejected with -EBUSY.

Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/vfio/pci/vfio_pci_core.c   | 7 +++++++
 drivers/vfio/pci/vfio_pci_dmabuf.c | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 1e922e3aaeb3..9cf494b765e7 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1828,6 +1828,13 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
 	if (!vdev->bar_mmap_supported[index])
 		return -EINVAL;
 
+	if (vdev->p2p_registered_bars & (1 << index)) {
+		pci_warn(vdev->pdev,
+			 "BAR %d registered for P2P. Use sysfs to allocate\n",
+			 index);
+		return -EBUSY;
+	}
+
 	phys_len = PAGE_ALIGN(pci_resource_len(pdev, index));
 	req_len = vma->vm_end - vma->vm_start;
 	pgoff = vma->vm_pgoff &
diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index c16f460c01d6..6635a8681291 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -251,6 +251,12 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
 	    IS_ERR(vfio_pci_core_get_iomap(vdev, get_dma_buf.region_index)))
 		return -ENODEV;
 
+	if (vdev->p2p_registered_bars & (1 << get_dma_buf.region_index)) {
+		pci_warn(vdev->pdev, "BAR %d registered for native P2P. Use sysfs for allocation.\n",
+			 get_dma_buf.region_index);
+		return -EBUSY;
+	}
+
 	dma_ranges = memdup_array_user(&arg->dma_ranges, get_dma_buf.nr_ranges,
 				       sizeof(*dma_ranges));
 	if (IS_ERR(dma_ranges))
-- 
2.54.0.1099.g489fc7bff1-goog