[PATCH] 8259 timer ack fix

From: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>

Fix up the 8259 ack handling for buggy SMM firmware.

See http://www.ussg.iu.edu/hypermail/linux/kernel/0203.2/0956.html

Apparently the embedded 8259A-compatible core is not fully functional.
This patch lets the I/O APIC-driven NMI watchdog to function correctly.
Credit to Ross Dickson for discovering this.

arch/i386/kernel/io_apic.c

@@ -2150,6 +2150,10 @@ static inline void check_timer(void)
 {
 	int pin1, pin2;
 	int vector;
+	unsigned int ver;
+
+	ver = apic_read(APIC_LVR);
+	ver = GET_APIC_VERSION(ver);
 
 	/*
 	 * get/set the timer IRQ vector:
@@ -2163,11 +2167,17 @@ static inline void check_timer(void)
 	 * mode for the 8259A whenever interrupts are routed
 	 * through I/O APICs.  Also IRQ0 has to be enabled in
 	 * the 8259A which implies the virtual wire has to be
-	 * disabled in the local APIC.
+	 * disabled in the local APIC.  Finally timer interrupts
+	 * need to be acknowledged manually in the 8259A for
+	 * do_slow_timeoffset() and for the i82489DX when using
+	 * the NMI watchdog.
 	 */
 	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
 	init_8259A(1);
+	if (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver))
 		timer_ack = 1;
+	else
+		timer_ack = !cpu_has_tsc;
 	enable_8259A_irq(0);
 
 	pin1 = find_isa_irq_pin(0, mp_INT);
@@ -2185,7 +2195,8 @@ static inline void check_timer(void)
 				disable_8259A_irq(0);
 				setup_nmi();
 				enable_8259A_irq(0);
-				check_nmi_watchdog();
+				if (check_nmi_watchdog() < 0);
+					timer_ack = !cpu_has_tsc;
 			}
 			return;
 		}
@@ -2208,7 +2219,8 @@ static inline void check_timer(void)
 				add_pin_to_irq(0, 0, pin2);
 			if (nmi_watchdog == NMI_IO_APIC) {
 				setup_nmi();
-				check_nmi_watchdog();
+				if (check_nmi_watchdog() < 0);
+					timer_ack = !cpu_has_tsc;
 			}
 			return;
 		}