[PATCH kernel] vfio_pci_nvlink2: Do not attempt NPU2 setup on old P8's NPU

[Alexey Kardashevskiy <aik@ozlabs.ru>]

We execute certain NPU2 setup code (such as mapping an LPID to a device
in NPU2) unconditionally if an Nvlink bridge is detected. However this
cannot succeed on P8+ machines as the init helpers return an error other
than ENODEV which means the device is there is and setup failed so
vfio_pci_enable() fails and pass through is not possible.

This changes the two NPU2 related init helpers to return -ENODEV if
there is no "memory-region" device tree property as this is
the distinction between NPU and NPU2.

Fixes: 7f92891778df ("vfio_pci: Add NVIDIA GV100GL [Tesla V100 SXM2] subdriver")
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
 drivers/vfio/pci/vfio_pci_nvlink2.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_nvlink2.c b/drivers/vfio/pci/vfio_pci_nvlink2.c
index 65c61710c0e9..9adcf6a8f888 100644
--- a/drivers/vfio/pci/vfio_pci_nvlink2.c
+++ b/drivers/vfio/pci/vfio_pci_nvlink2.c
@@ -231,7 +231,7 @@ int vfio_pci_nvdia_v100_nvlink2_init(struct vfio_pci_device *vdev)
 		return -EINVAL;
 
 	if (of_property_read_u32(npu_node, "memory-region", &mem_phandle))
-		return -EINVAL;
+		return -ENODEV;
 
 	mem_node = of_find_node_by_phandle(mem_phandle);
 	if (!mem_node)
@@ -393,7 +393,7 @@ int vfio_pci_ibm_npu2_init(struct vfio_pci_device *vdev)
 	int ret;
 	struct vfio_pci_npu2_data *data;
 	struct device_node *nvlink_dn;
-	u32 nvlink_index = 0;
+	u32 nvlink_index = 0, mem_phandle = 0;
 	struct pci_dev *npdev = vdev->pdev;
 	struct device_node *npu_node = pci_device_to_OF_node(npdev);
 	struct pci_controller *hose = pci_bus_to_host(npdev->bus);
@@ -408,6 +408,9 @@ int vfio_pci_ibm_npu2_init(struct vfio_pci_device *vdev)
 	if (!pnv_pci_get_gpu_dev(vdev->pdev))
 		return -ENODEV;
 
+	if (of_property_read_u32(npu_node, "memory-region", &mem_phandle))
+		return -ENODEV;
+
 	/*
 	 * NPU2 normally has 8 ATSD registers (for concurrency) and 6 links
 	 * so we can allocate one register per link, using nvlink index as
-- 
2.17.1