--- sys/i386/pci/pci_pir.c.orig	2009-10-11 02:59:35.000000000 +0800
+++ sys/i386/pci/pci_pir.c	2009-10-11 03:58:48.000000000 +0800
@@ -123,6 +123,12 @@
     "Mask of allowed irqs to try to route when it has no good clue about\n"
     "which irqs it should use.");
 
+static uint32_t pir_checksum_ignore = 0;
+TUNABLE_INT("hw.pci.pir_checksum_ignore", &pir_checksum_ignore);
+SYSCTL_INT(_hw_pci, OID_AUTO, pir_checksum_ignore, CTLFLAG_RDTUN,
+    &pir_checksum_ignore, 0,
+    "Ignore incorrect checksum of PCI BIOS's PIR table");
+
 /*
  * Look for the interrupt routing table.
  *
@@ -160,8 +166,14 @@
 	for (cv = (u_int8_t *)pt, ck = 0, i = 0;
 	     i < (pt->pt_header.ph_length); i++)
 		ck += cv[i];
-	if (ck != 0)
+	if (ck != 0) {
+	  if (bootverbose)
+		printf("$PIR: checksum %#04x incorrect, %s\n",
+			(unsigned)ck,
+			pir_checksum_ignore ? "using anyway" : "table ignored");
+	  if (!pir_checksum_ignore)
 		return;
+	}
 
 	/* Ok, we've got a valid table. */
 	pci_route_table = pt;