Index: sys/arm64/arm64/gic_v3_its.c
===================================================================
--- sys/arm64/arm64/gic_v3_its.c
+++ sys/arm64/arm64/gic_v3_its.c
@@ -61,6 +61,7 @@
 
 #define	GIC_V3_ITS_QUIRK_THUNDERX_PEM_BUS_OFFSET	88
 
+#include "pcib_if.h"
 #include "pic_if.h"
 
 /* Device and PIC methods */
@@ -1574,14 +1575,34 @@
 static uint32_t
 its_get_devid_thunder(device_t pci_dev)
 {
+	devclass_t pci_class;
+	device_t pci_parent;
+	boolean_t ari_enabled;
+	uint32_t bus;
 	int bsf;
 	int pem;
-	uint32_t bus;
+
+	/* Check if ARI enabled on this bus */
+	pci_class = devclass_find("pci");
+	pci_parent = device_get_parent(pci_dev);
+	KASSERT(device_get_devclass(pci_parent) == pci_class,
+	    ("%s: non-pci device requested LPI", __func__));
+	ari_enabled = PCIB_ARI_ENABLED(device_get_parent(pci_parent));
 
 	bus = pci_get_bus(pci_dev);
 
-	bsf = PCI_RID(pci_get_bus(pci_dev), pci_get_slot(pci_dev),
-	    pci_get_function(pci_dev));
+	if (ari_enabled) {
+		/*
+		 * For ARI enabled device/slot is ignored
+		 * and function/identifier is extended to 8 bits
+		 */
+		bsf =
+		    ((pci_get_bus(pci_dev) & PCI_BUSMAX) << PCI_RID_BUS_SHIFT) |
+		    ((pci_get_function(pci_dev) & PCIE_ARI_FUNCMAX) << PCI_RID_FUNC_SHIFT);
+	} else {
+		bsf = PCI_RID(pci_get_bus(pci_dev), pci_get_slot(pci_dev),
+		    pci_get_function(pci_dev));
+	}
 
 	/* Check if accessing internal PCIe (low bus numbers) */
 	if (bus < GIC_V3_ITS_QUIRK_THUNDERX_PEM_BUS_OFFSET) {