Commit e46cdb66 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Jeremy Fitzhardinge
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xen: event channels



Xen implements interrupts in terms of event channels.  Each guest
domain gets 1024 event channels which can be used for a variety of
purposes, such as Xen timer events, inter-domain events,
inter-processor events (IPI) or for real hardware IRQs.

Within the kernel, we map the event channels to IRQs, and implement
the whole interrupt handling using a Xen irq_chip.

Rather than setting NR_IRQ to 1024 under PARAVIRT in order to
accomodate Xen, we create a dynamic mapping between event channels and
IRQs.  Ideally, Linux will eventually move towards dynamically
allocating per-irq structures, and we can use a 1:1 mapping between
event channels and irqs.
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Eric W. Biederman <ebiederm@xmission.com>
parent 3b827c1b
obj-y := enlighten.o setup.o features.o multicalls.o mmu.o
obj-y := enlighten.o setup.o features.o multicalls.o mmu.o \
events.o
......@@ -607,6 +607,7 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
.memory_setup = xen_memory_setup,
.arch_setup = xen_arch_setup,
.init_IRQ = xen_init_IRQ,
.cpuid = xen_cpuid,
......
/*
* Xen event channels
*
* Xen models interrupts with abstract event channels. Because each
* domain gets 1024 event channels, but NR_IRQ is not that large, we
* must dynamically map irqs<->event channels. The event channels
* interface with the rest of the kernel by defining a xen interrupt
* chip. When an event is recieved, it is mapped to an irq and sent
* through the normal interrupt processing path.
*
* There are four kinds of events which can be mapped to an event
* channel:
*
* 1. Inter-domain notifications. This includes all the virtual
* device events, since they're driven by front-ends in another domain
* (typically dom0).
* 2. VIRQs, typically used for timers. These are per-cpu events.
* 3. IPIs.
* 4. Hardware interrupts. Not supported at present.
*
* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
*/
#include <linux/linkage.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/string.h>
#include <asm/ptrace.h>
#include <asm/irq.h>
#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>
#include "xen-ops.h"
/*
* This lock protects updates to the following mapping and reference-count
* arrays. The lock does not need to be acquired to read the mapping tables.
*/
static DEFINE_SPINLOCK(irq_mapping_update_lock);
/* IRQ <-> VIRQ mapping. */
static DEFINE_PER_CPU(int, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};
/* Packed IRQ information: binding type, sub-type index, and event channel. */
struct packed_irq
{
unsigned short evtchn;
unsigned char index;
unsigned char type;
};
static struct packed_irq irq_info[NR_IRQS];
/* Binding types. */
enum { IRQT_UNBOUND, IRQT_PIRQ, IRQT_VIRQ, IRQT_IPI, IRQT_EVTCHN };
/* Convenient shorthand for packed representation of an unbound IRQ. */
#define IRQ_UNBOUND mk_irq_info(IRQT_UNBOUND, 0, 0)
static int evtchn_to_irq[NR_EVENT_CHANNELS] = {
[0 ... NR_EVENT_CHANNELS-1] = -1
};
static unsigned long cpu_evtchn_mask[NR_CPUS][NR_EVENT_CHANNELS/BITS_PER_LONG];
static u8 cpu_evtchn[NR_EVENT_CHANNELS];
/* Reference counts for bindings to IRQs. */
static int irq_bindcount[NR_IRQS];
/* Xen will never allocate port zero for any purpose. */
#define VALID_EVTCHN(chn) ((chn) != 0)
/*
* Force a proper event-channel callback from Xen after clearing the
* callback mask. We do this in a very simple manner, by making a call
* down into Xen. The pending flag will be checked by Xen on return.
*/
void force_evtchn_callback(void)
{
(void)HYPERVISOR_xen_version(0, NULL);
}
EXPORT_SYMBOL_GPL(force_evtchn_callback);
static struct irq_chip xen_dynamic_chip;
/* Constructor for packed IRQ information. */
static inline struct packed_irq mk_irq_info(u32 type, u32 index, u32 evtchn)
{
return (struct packed_irq) { evtchn, index, type };
}
/*
* Accessors for packed IRQ information.
*/
static inline unsigned int evtchn_from_irq(int irq)
{
return irq_info[irq].evtchn;
}
static inline unsigned int index_from_irq(int irq)
{
return irq_info[irq].index;
}
static inline unsigned int type_from_irq(int irq)
{
return irq_info[irq].type;
}
static inline unsigned long active_evtchns(unsigned int cpu,
struct shared_info *sh,
unsigned int idx)
{
return (sh->evtchn_pending[idx] &
cpu_evtchn_mask[cpu][idx] &
~sh->evtchn_mask[idx]);
}
static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
{
int irq = evtchn_to_irq[chn];
BUG_ON(irq == -1);
#ifdef CONFIG_SMP
irq_desc[irq].affinity = cpumask_of_cpu(cpu);
#endif
__clear_bit(chn, cpu_evtchn_mask[cpu_evtchn[chn]]);
__set_bit(chn, cpu_evtchn_mask[cpu]);
cpu_evtchn[chn] = cpu;
}
static void init_evtchn_cpu_bindings(void)
{
#ifdef CONFIG_SMP
int i;
/* By default all event channels notify CPU#0. */
for (i = 0; i < NR_IRQS; i++)
irq_desc[i].affinity = cpumask_of_cpu(0);
#endif
memset(cpu_evtchn, 0, sizeof(cpu_evtchn));
memset(cpu_evtchn_mask[0], ~0, sizeof(cpu_evtchn_mask[0]));
}
static inline unsigned int cpu_from_evtchn(unsigned int evtchn)
{
return cpu_evtchn[evtchn];
}
static inline void clear_evtchn(int port)
{
struct shared_info *s = HYPERVISOR_shared_info;
sync_clear_bit(port, &s->evtchn_pending[0]);
}
static inline void set_evtchn(int port)
{
struct shared_info *s = HYPERVISOR_shared_info;
sync_set_bit(port, &s->evtchn_pending[0]);
}
/**
* notify_remote_via_irq - send event to remote end of event channel via irq
* @irq: irq of event channel to send event to
*
* Unlike notify_remote_via_evtchn(), this is safe to use across
* save/restore. Notifications on a broken connection are silently
* dropped.
*/
void notify_remote_via_irq(int irq)
{
int evtchn = evtchn_from_irq(irq);
if (VALID_EVTCHN(evtchn))
notify_remote_via_evtchn(evtchn);
}
EXPORT_SYMBOL_GPL(notify_remote_via_irq);
static void mask_evtchn(int port)
{
struct shared_info *s = HYPERVISOR_shared_info;
sync_set_bit(port, &s->evtchn_mask[0]);
}
static void unmask_evtchn(int port)
{
struct shared_info *s = HYPERVISOR_shared_info;
unsigned int cpu = get_cpu();
BUG_ON(!irqs_disabled());
/* Slow path (hypercall) if this is a non-local port. */
if (unlikely(cpu != cpu_from_evtchn(port))) {
struct evtchn_unmask unmask = { .port = port };
(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
} else {
struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
sync_clear_bit(port, &s->evtchn_mask[0]);
/*
* The following is basically the equivalent of
* 'hw_resend_irq'. Just like a real IO-APIC we 'lose
* the interrupt edge' if the channel is masked.
*/
if (sync_test_bit(port, &s->evtchn_pending[0]) &&
!sync_test_and_set_bit(port / BITS_PER_LONG,
&vcpu_info->evtchn_pending_sel))
vcpu_info->evtchn_upcall_pending = 1;
}
put_cpu();
}
static int find_unbound_irq(void)
{
int irq;
/* Only allocate from dynirq range */
for (irq = 0; irq < NR_IRQS; irq++)
if (irq_bindcount[irq] == 0)
break;
if (irq == NR_IRQS)
panic("No available IRQ to bind to: increase NR_IRQS!\n");
return irq;
}
static int bind_evtchn_to_irq(unsigned int evtchn)
{
int irq;
spin_lock(&irq_mapping_update_lock);
irq = evtchn_to_irq[evtchn];
if (irq == -1) {
irq = find_unbound_irq();
dynamic_irq_init(irq);
set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
handle_level_irq, "event");
evtchn_to_irq[evtchn] = irq;
irq_info[irq] = mk_irq_info(IRQT_EVTCHN, 0, evtchn);
}
irq_bindcount[irq]++;
spin_unlock(&irq_mapping_update_lock);
return irq;
}
static int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
{
struct evtchn_bind_virq bind_virq;
int evtchn, irq;
spin_lock(&irq_mapping_update_lock);
irq = per_cpu(virq_to_irq, cpu)[virq];
if (irq == -1) {
bind_virq.virq = virq;
bind_virq.vcpu = cpu;
if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
&bind_virq) != 0)
BUG();
evtchn = bind_virq.port;
irq = find_unbound_irq();
dynamic_irq_init(irq);
set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
handle_level_irq, "virq");
evtchn_to_irq[evtchn] = irq;
irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);
per_cpu(virq_to_irq, cpu)[virq] = irq;
bind_evtchn_to_cpu(evtchn, cpu);
}
irq_bindcount[irq]++;
spin_unlock(&irq_mapping_update_lock);
return irq;
}
static void unbind_from_irq(unsigned int irq)
{
struct evtchn_close close;
int evtchn = evtchn_from_irq(irq);
spin_lock(&irq_mapping_update_lock);
if (VALID_EVTCHN(evtchn) && (--irq_bindcount[irq] == 0)) {
close.port = evtchn;
if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
BUG();
switch (type_from_irq(irq)) {
case IRQT_VIRQ:
per_cpu(virq_to_irq, cpu_from_evtchn(evtchn))
[index_from_irq(irq)] = -1;
break;
default:
break;
}
/* Closed ports are implicitly re-bound to VCPU0. */
bind_evtchn_to_cpu(evtchn, 0);
evtchn_to_irq[evtchn] = -1;
irq_info[irq] = IRQ_UNBOUND;
dynamic_irq_init(irq);
}
spin_unlock(&irq_mapping_update_lock);
}
int bind_evtchn_to_irqhandler(unsigned int evtchn,
irqreturn_t (*handler)(int, void *),
unsigned long irqflags,
const char *devname, void *dev_id)
{
unsigned int irq;
int retval;
irq = bind_evtchn_to_irq(evtchn);
retval = request_irq(irq, handler, irqflags, devname, dev_id);
if (retval != 0) {
unbind_from_irq(irq);
return retval;
}
return irq;
}
EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler);
int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
irqreturn_t (*handler)(int, void *),
unsigned long irqflags, const char *devname, void *dev_id)
{
unsigned int irq;
int retval;
irq = bind_virq_to_irq(virq, cpu);
retval = request_irq(irq, handler, irqflags, devname, dev_id);
if (retval != 0) {
unbind_from_irq(irq);
return retval;
}
return irq;
}
EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);
void unbind_from_irqhandler(unsigned int irq, void *dev_id)
{
free_irq(irq, dev_id);
unbind_from_irq(irq);
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
/*
* Search the CPUs pending events bitmasks. For each one found, map
* the event number to an irq, and feed it into do_IRQ() for
* handling.
*
* Xen uses a two-level bitmap to speed searching. The first level is
* a bitset of words which contain pending event bits. The second
* level is a bitset of pending events themselves.
*/
fastcall void xen_evtchn_do_upcall(struct pt_regs *regs)
{
int cpu = get_cpu();
struct shared_info *s = HYPERVISOR_shared_info;
struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
unsigned long pending_words;
vcpu_info->evtchn_upcall_pending = 0;
/* NB. No need for a barrier here -- XCHG is a barrier on x86. */
pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
while (pending_words != 0) {
unsigned long pending_bits;
int word_idx = __ffs(pending_words);
pending_words &= ~(1UL << word_idx);
while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
int bit_idx = __ffs(pending_bits);
int port = (word_idx * BITS_PER_LONG) + bit_idx;
int irq = evtchn_to_irq[port];
if (irq != -1) {
regs->orig_eax = ~irq;
do_IRQ(regs);
}
}
}
put_cpu();
}
/* Rebind an evtchn so that it gets delivered to a specific cpu */
static void rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
{
struct evtchn_bind_vcpu bind_vcpu;
int evtchn = evtchn_from_irq(irq);
if (!VALID_EVTCHN(evtchn))
return;
/* Send future instances of this interrupt to other vcpu. */
bind_vcpu.port = evtchn;
bind_vcpu.vcpu = tcpu;
/*
* If this fails, it usually just indicates that we're dealing with a
* virq or IPI channel, which don't actually need to be rebound. Ignore
* it, but don't do the xenlinux-level rebind in that case.
*/
if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
bind_evtchn_to_cpu(evtchn, tcpu);
}
static void set_affinity_irq(unsigned irq, cpumask_t dest)
{
unsigned tcpu = first_cpu(dest);
rebind_irq_to_cpu(irq, tcpu);
}
static void enable_dynirq(unsigned int irq)
{
int evtchn = evtchn_from_irq(irq);
if (VALID_EVTCHN(evtchn))
unmask_evtchn(evtchn);
}
static void disable_dynirq(unsigned int irq)
{
int evtchn = evtchn_from_irq(irq);
if (VALID_EVTCHN(evtchn))
mask_evtchn(evtchn);
}
static void ack_dynirq(unsigned int irq)
{
int evtchn = evtchn_from_irq(irq);
move_native_irq(irq);
if (VALID_EVTCHN(evtchn))
clear_evtchn(evtchn);
}
static int retrigger_dynirq(unsigned int irq)
{
int evtchn = evtchn_from_irq(irq);
int ret = 0;
if (VALID_EVTCHN(evtchn)) {
set_evtchn(evtchn);
ret = 1;
}
return ret;
}
static struct irq_chip xen_dynamic_chip __read_mostly = {
.name = "xen-dyn",
.mask = disable_dynirq,
.unmask = enable_dynirq,
.ack = ack_dynirq,
.set_affinity = set_affinity_irq,
.retrigger = retrigger_dynirq,
};
void __init xen_init_IRQ(void)
{
int i;
init_evtchn_cpu_bindings();
/* No event channels are 'live' right now. */
for (i = 0; i < NR_EVENT_CHANNELS; i++)
mask_evtchn(i);
/* Dynamic IRQ space is currently unbound. Zero the refcnts. */
for (i = 0; i < NR_IRQS; i++)
irq_bindcount[i] = 0;
irq_ctx_init(smp_processor_id());
}
#ifndef _XEN_EVENTS_H
#define _XEN_EVENTS_H
#include <linux/irq.h>
int bind_evtchn_to_irqhandler(unsigned int evtchn,
irqreturn_t (*handler)(int, void *),
unsigned long irqflags, const char *devname,
void *dev_id);
int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
irqreturn_t (*handler)(int, void *),
unsigned long irqflags, const char *devname, void *dev_id);
/*
* Common unbind function for all event sources. Takes IRQ to unbind from.
* Automatically closes the underlying event channel (even for bindings
* made with bind_evtchn_to_irqhandler()).
*/
void unbind_from_irqhandler(unsigned int irq, void *dev_id);
static inline void notify_remote_via_evtchn(int port)
{
struct evtchn_send send = { .port = port };
(void)HYPERVISOR_event_channel_op(EVTCHNOP_send, &send);
}
extern void notify_remote_via_irq(int irq);
#endif /* _XEN_EVENTS_H */
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