diff --git a/sys/dev/pci/pcireg.h b/sys/dev/pci/pcireg.h
--- a/sys/dev/pci/pcireg.h
+++ b/sys/dev/pci/pcireg.h
@@ -1098,3 +1098,28 @@
 #define	PCIM_OSC_CTL_PCIE_PME		0x04	/* PCIe Native Power Mgt Events */
 #define	PCIM_OSC_CTL_PCIE_AER		0x08	/* PCIe Advanced Error Reporting */
 #define	PCIM_OSC_CTL_PCIE_CAP_STRUCT	0x10	/* Various Capability Structures */
+
+/* Access Control Services (ACS) definitions */
+#define	PCIR_ACS_CAP	0x4
+#define	PCIM_ACS_SOURCE_VALIDATION		0x0001
+#define	PCIM_ACS_TRANSLATION_BLOCKING		0x0002
+#define	PCIM_ACS_P2P_REQ_REDIRECT		0x0004
+#define	PCIM_ACS_P2P_CMP_REDIRECT		0x0008
+#define	PCIM_ACS_P2P_UPSTREAM_FORWARDING	0x0010
+#define	PCIM_ACS_P2P_EGRESS_CTL			0x0020
+#define	PCIM_ACS_P2P_DIRECT_TRANSLATED		0x0040
+#define	PCIM_ACS_ENHANCED_CAP			0x0080
+#define	PCIM_ACS_EGRESS_CTL_VECTOR_SIZE		0xff00
+#define	PCIR_ACS_CTL	0x6
+#define	PCIM_ACS_SOURCE_VALIDATION_ENABLE	0x0001
+#define	PCIM_ACS_TRANSLATION_BLOCKING_ENABLE	0x0002
+#define	PCIM_ACS_P2P_REQ_REDIRECT_ENABLE	0x0004
+#define	PCIM_ACS_P2P_CMP_REDIRECT_ENABLE	0x0008
+#define	PCIM_ACS_P2P_UPSTREAM_FORWARDING_ENABLE	0x0010
+#define	PCIM_ACS_P2P_EGRESS_CTL_ENABLE		0x0020
+#define	PCIM_ACS_P2P_DIRECT_TRANSLATED_ENABLE	0x0040
+#define	PCIM_ACS_IO_REQ_BLOCKING_ENABLE		0x0080
+#define	PCIM_ACS_DSP_MEM_TGT_ACC_CTL		0x0300
+#define	PCIM_ACS_USP_MEM_TGT_ACC_CTL		0x0c00
+#define	PCIM_ACS_UNCLAIMED_REQ_REDIRECT_CTL	0x1000
+#define	PCIR_ACS_EGRESS_CONTROL_VECTOR	0x8