Big fixes for the new IO-APIC acknowledging method. The problems

were:
 1. Some critical Xen interrupts could get blocked behind
    unacknowledged guest interrupts. This is avoided by making
    all Xen-bound interrrupts strictly higher priority.
 2. Interrupts must not only be EOIed on the CPU that received
    them, but also in reverse order when interrupts are nested.
    A whole load of logic has been added to ensure this.

There are two boot parameters relating to all this:
 'ioapic_ack=old' -- use the old IO-APIC ACK method
 'ioapic_ack=new' -- use the new IO-APIC ACK method (default)
 'force_intack'   -- periodically force acknowledgement of
                     interrupts (default is no; useful for debugging)

Signed-off-by: Keir Fraser <keir@xensource.com>

2 files changed, 17 insertions, 85 deletions

diff --git a/xen/include/asm-x86/mach-default/irq_vectors.h b/xen/include/asm-x86/mach-default/irq_vectors.h
index de16b5bc9c..34a963a534 100644
--- a/xen/include/asm-x86/mach-default/irq_vectors.h
+++ b/xen/include/asm-x86/mach-default/irq_vectors.h
@@ -1,96 +1,36 @@
-/*
- * This file should contain #defines for all of the interrupt vector
- * numbers used by this architecture.
- *
- * In addition, there are some standard defines:
- *
- *	FIRST_EXTERNAL_VECTOR:
- *		The first free place for external interrupts
- *
- *	SYSCALL_VECTOR:
- *		The IRQ vector a syscall makes the user to kernel transition
- *		under.
- *
- *	TIMER_IRQ:
- *		The IRQ number the timer interrupt comes in at.
- *
- *	NR_IRQS:
- *		The total number of interrupt vectors (including all the
- *		architecture specific interrupts) needed.
- *
- */			
 #ifndef _ASM_IRQ_VECTORS_H
 #define _ASM_IRQ_VECTORS_H
 
-/*
- * IDT vectors usable for external interrupt sources start
- * at 0x20:
- */
-#define FIRST_EXTERNAL_VECTOR	0x20
-
-#define HYPERCALL_VECTOR	0x82
-
-/*
- * Vectors 0x20-0x2f are used for ISA interrupts.
- */
-
-/*
- * Special IRQ vectors used by the SMP architecture, 0xf0-0xff
- *
- *  some of the following vectors are 'rare', they are merged
- *  into a single vector (CALL_FUNCTION_VECTOR) to save vector space.
- *  TLB, reschedule and local APIC vectors are performance-critical.
- *
- *  Vectors 0xf0-0xfa are free (reserved for future Linux use).
- */
+/* Processor-initiated interrupts are all high priority. */
 #define SPURIOUS_APIC_VECTOR	0xff
 #define ERROR_APIC_VECTOR	0xfe
 #define INVALIDATE_TLB_VECTOR	0xfd
 #define EVENT_CHECK_VECTOR	0xfc
 #define CALL_FUNCTION_VECTOR	0xfb
+#define THERMAL_APIC_VECTOR	0xfa
+#define LOCAL_TIMER_VECTOR	0xf9
 
-#define THERMAL_APIC_VECTOR	0xf0
 /*
- * Local APIC timer IRQ vector is on a different priority level,
- * to work around the 'lost local interrupt if more than 2 IRQ
- * sources per level' errata.
+ * High-priority dynamically-allocated vectors. For interrupts that
+ * must be higher priority than any guest-bound interrupt.
  */
-#define LOCAL_TIMER_VECTOR	0xef
+#define FIRST_HIPRIORITY_VECTOR	0xf0
+#define LAST_HIPRIORITY_VECTOR  0xf8
 
-/*
- * First APIC vector available to drivers: (vectors 0x30-0xee)
- * we start at 0x31 to spread out vectors evenly between priority
- * levels. (0x80 is the syscall vector)
- */
-#define FIRST_DEVICE_VECTOR	0x31
-#define FIRST_SYSTEM_VECTOR	0xef
+/* Legacy PIC uses vectors 0xe0-0xef. */
+#define FIRST_LEGACY_VECTOR	0xe0
+#define LAST_LEGACY_VECTOR      0xef
 
-#define TIMER_IRQ 0
+#define HYPERCALL_VECTOR	0x82
 
-/*
- * 16 8259A IRQ's, 208 potential APIC interrupt sources.
- * Right now the APIC is mostly only used for SMP.
- * 256 vectors is an architectural limit. (we can have
- * more than 256 devices theoretically, but they will
- * have to use shared interrupts)
- * Since vectors 0x00-0x1f are used/reserved for the CPU,
- * the usable vector space is 0x20-0xff (224 vectors)
- */
+/* Dynamically-allocated vectors available to any driver. */
+#define FIRST_DYNAMIC_VECTOR	0x20
+#define LAST_DYNAMIC_VECTOR	0xdf
 
-/*
- * The maximum number of vectors supported by i386 processors
- * is limited to 256. For processors other than i386, NR_VECTORS
- * should be changed accordingly.
- */
 #define NR_VECTORS 256
 
-#include "irq_vectors_limits.h"
-
-#define FPU_IRQ			13
-
-#define	FIRST_VM86_IRQ		3
-#define LAST_VM86_IRQ		15
-#define invalid_vm86_irq(irq)	((irq) < 3 || (irq) > 15)
-
+/* Limited by number of trap vectors. */
+#define NR_IRQS        NR_VECTORS
+#define NR_IRQ_VECTORS NR_IRQS
 
 #endif /* _ASM_IRQ_VECTORS_H */
diff --git a/xen/include/asm-x86/mach-default/irq_vectors_limits.h b/xen/include/asm-x86/mach-default/irq_vectors_limits.h
deleted file mode 100644
index 11e263cb18..0000000000
--- a/xen/include/asm-x86/mach-default/irq_vectors_limits.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef _ASM_IRQ_VECTORS_LIMITS_H
-#define _ASM_IRQ_VECTORS_LIMITS_H
-
-/* Limited by number of trap vectors. */
-#define NR_IRQS        FIRST_SYSTEM_VECTOR
-#define NR_IRQ_VECTORS NR_IRQS
-
-#endif /* _ASM_IRQ_VECTORS_LIMITS_H */