They apparently leave the USB legacy emulation bits set in ICH10's
SMI Control and Enable register, but fail to handle the resulting SMIs
gracefully. The hangs can apparently extend indefinitely, but are
commonly observed to last between a few seconds and a minute.

This assumes that only ICH10-based systems on Intel main boards with
Intel BIOS may be affected. Until Intel comes up with a more precise
identification of affected BIOSes, all Intel ones on Intel boards
will get this workaround applied.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- a/xen/arch/x86/dmi_scan.c
+++ b/xen/arch/x86/dmi_scan.c
@@ -10,6 +10,8 @@
 #include <asm/system.h>
 #include <xen/dmi.h>
 #include <xen/efi.h>
+#include <xen/pci.h>
+#include <xen/pci_regs.h>
 
 #define bt_ioremap(b,l)  ((void *)__acpi_map_table(b,l))
 #define bt_iounmap(b,l)  ((void)0)
@@ -278,6 +280,28 @@ static __init int broken_toshiba_keyboar
 	return 0;
 }
 
+static int __init ich10_bios_quirk(struct dmi_system_id *d)
+{
+    u32 port, smictl;
+
+    if ( pci_conf_read16(0, 0x1f, 0, PCI_VENDOR_ID) != 0x8086 )
+        return 0;
+
+    switch ( pci_conf_read16(0, 0x1f, 0, PCI_DEVICE_ID) ) {
+    case 0x3a14:
+    case 0x3a16:
+    case 0x3a18:
+    case 0x3a1a:
+        port = (pci_conf_read16(0, 0x1f, 0, 0x40) & 0xff80) + 0x30;
+        smictl = inl(port);
+        /* turn off LEGACY_USB{,2}_EN if enabled */
+        if ( smictl & 0x20008 )
+            outl(smictl & ~0x20008, port);
+        break;
+    }
+
+    return 0;
+}
 
 #ifdef CONFIG_ACPI_SLEEP
 static __init int reset_videomode_after_s3(struct dmi_blacklist *d)
@@ -342,6 +369,18 @@ static __initdata struct dmi_blacklist d
 			} },
 #endif
 
+	{ ich10_bios_quirk, "Intel board & BIOS",
+		/*
+		 * BIOS leaves legacy USB emulation enabled while
+		 * SMM can't properly handle it.
+		 */
+		{
+			MATCH(DMI_BOARD_VENDOR, "Intel Corp"),
+			MATCH(DMI_BIOS_VENDOR, "Intel Corp"),
+			NO_MATCH, NO_MATCH
+		}
+	},
+
 #ifdef	CONFIG_ACPI_BOOT
 	/*
 	 * If your system is blacklisted here, but you find that acpi=force