Index: sys/amd64/pci/pci_cfgreg.c
===================================================================
--- sys/amd64/pci/pci_cfgreg.c
+++ sys/amd64/pci/pci_cfgreg.c
@@ -64,6 +64,7 @@
 static int pcie_minbus, pcie_maxbus;
 static uint32_t pcie_badslots;
 static struct mtx pcicfg_mtx;
+MTX_SYSINIT(pcicfg_mtx, &pcicfg_mtx, "pcicfg_mtx", MTX_SPIN);
 static int mcfg_enable = 1;
 SYSCTL_INT(_hw_pci, OID_AUTO, mcfg, CTLFLAG_RDTUN, &mcfg_enable, 0,
     "Enable support for PCI-e memory mapped config access");
@@ -74,15 +75,9 @@
 int
 pci_cfgregopen(void)
 {
-	static int once = 0;
 	uint64_t pciebar;
 	uint16_t did, vid;
 
-	if (!once) {
-		mtx_init(&pcicfg_mtx, "pcicfg", NULL, MTX_SPIN);
-		once = 1;
-	}
-
 	if (cfgmech != CFGMECH_NONE)
 		return (1);
 	cfgmech = CFGMECH_1;
@@ -138,6 +133,9 @@
 {
 	uint32_t line;
 
+	if (cfgmech == CFGMECH_NONE)
+		return (0xffffffff);
+
 	/*
 	 * Some BIOS writers seem to want to ignore the spec and put
 	 * 0 in the intline rather than 255 to indicate none.  Some use
@@ -162,6 +160,9 @@
 pci_cfgregwrite(int bus, int slot, int func, int reg, u_int32_t data, int bytes)
 {
 
+	if (cfgmech == CFGMECH_NONE)
+		return;
+
 	if (cfgmech == CFGMECH_PCIE &&
 	    (bus >= pcie_minbus && bus <= pcie_maxbus) &&
 	    (bus != 0 || !(1 << slot & pcie_badslots)))