[PATCH v2 3/5] PCI/ATS: Skip VF ATS initialization if PF does not implement it

[sathyanarayanan . kuppuswamy]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>

If PF does not implement ATS and VF implements/uses it, it might lead to
runtime issues. Also, as per spec r4.0, sec 9.3.7.8, PF should implement
ATS if VF implements it. So add additional check to confirm given device
aligns with the spec.

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Keith Busch <keith.busch@xxxxxxxxx>
Suggested-by: Ashok Raj <ashok.raj@xxxxxxxxx>
Reviewed-by: Keith Busch <keith.busch@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
 drivers/pci/ats.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
index e7a904e347c3..718e6f414680 100644
--- a/drivers/pci/ats.c
+++ b/drivers/pci/ats.c
@@ -19,6 +19,7 @@
 void pci_ats_init(struct pci_dev *dev)
 {
 	int pos;
+	struct pci_dev *pdev;
 
 	if (pci_ats_disabled())
 		return;
@@ -27,6 +28,17 @@ void pci_ats_init(struct pci_dev *dev)
 	if (!pos)
 		return;
 
+	/*
+	 * Per PCIe r4.0, sec 9.3.7.8, if VF implements Address Translation
+	 * Services (ATS) Extended Capability then corresponding PF should
+	 * also implement it.
+	 */
+	if (dev->is_virtfn) {
+		pdev = pci_physfn(dev);
+		if (!pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ATS))
+			return;
+	}
+
 	dev->ats_cap = pos;
 }
 
-- 
2.20.1