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: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Jeremy Fitzhardinge
Jeremy Fitzhardinge
parent
3b827c1b3a
commit
e46cdb66c8
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@ -1 +1,2 @@
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obj-y := enlighten.o setup.o features.o multicalls.o mmu.o
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obj-y := enlighten.o setup.o features.o multicalls.o mmu.o \
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events.o
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@ -607,6 +607,7 @@ static const struct paravirt_ops xen_paravirt_ops __initdata = {
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.memory_setup = xen_memory_setup,
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.arch_setup = xen_arch_setup,
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.init_IRQ = xen_init_IRQ,
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.cpuid = xen_cpuid,
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@ -0,0 +1,511 @@
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/*
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* Xen event channels
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*
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* Xen models interrupts with abstract event channels. Because each
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* domain gets 1024 event channels, but NR_IRQ is not that large, we
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* must dynamically map irqs<->event channels. The event channels
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* interface with the rest of the kernel by defining a xen interrupt
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* chip. When an event is recieved, it is mapped to an irq and sent
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* through the normal interrupt processing path.
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*
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* There are four kinds of events which can be mapped to an event
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* channel:
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*
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* 1. Inter-domain notifications. This includes all the virtual
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* device events, since they're driven by front-ends in another domain
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* (typically dom0).
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* 2. VIRQs, typically used for timers. These are per-cpu events.
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* 3. IPIs.
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* 4. Hardware interrupts. Not supported at present.
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*
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* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
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*/
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#include <linux/linkage.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/module.h>
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#include <linux/string.h>
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#include <asm/ptrace.h>
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#include <asm/irq.h>
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#include <asm/sync_bitops.h>
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#include <asm/xen/hypercall.h>
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#include <xen/events.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/event_channel.h>
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#include "xen-ops.h"
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/*
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* This lock protects updates to the following mapping and reference-count
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* arrays. The lock does not need to be acquired to read the mapping tables.
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*/
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static DEFINE_SPINLOCK(irq_mapping_update_lock);
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/* IRQ <-> VIRQ mapping. */
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static DEFINE_PER_CPU(int, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};
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/* Packed IRQ information: binding type, sub-type index, and event channel. */
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struct packed_irq
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{
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unsigned short evtchn;
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unsigned char index;
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unsigned char type;
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};
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static struct packed_irq irq_info[NR_IRQS];
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/* Binding types. */
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enum { IRQT_UNBOUND, IRQT_PIRQ, IRQT_VIRQ, IRQT_IPI, IRQT_EVTCHN };
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/* Convenient shorthand for packed representation of an unbound IRQ. */
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#define IRQ_UNBOUND mk_irq_info(IRQT_UNBOUND, 0, 0)
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static int evtchn_to_irq[NR_EVENT_CHANNELS] = {
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[0 ... NR_EVENT_CHANNELS-1] = -1
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};
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static unsigned long cpu_evtchn_mask[NR_CPUS][NR_EVENT_CHANNELS/BITS_PER_LONG];
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static u8 cpu_evtchn[NR_EVENT_CHANNELS];
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/* Reference counts for bindings to IRQs. */
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static int irq_bindcount[NR_IRQS];
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/* Xen will never allocate port zero for any purpose. */
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#define VALID_EVTCHN(chn) ((chn) != 0)
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/*
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* Force a proper event-channel callback from Xen after clearing the
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* callback mask. We do this in a very simple manner, by making a call
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* down into Xen. The pending flag will be checked by Xen on return.
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*/
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void force_evtchn_callback(void)
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{
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(void)HYPERVISOR_xen_version(0, NULL);
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}
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EXPORT_SYMBOL_GPL(force_evtchn_callback);
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static struct irq_chip xen_dynamic_chip;
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/* Constructor for packed IRQ information. */
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static inline struct packed_irq mk_irq_info(u32 type, u32 index, u32 evtchn)
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{
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return (struct packed_irq) { evtchn, index, type };
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}
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/*
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* Accessors for packed IRQ information.
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*/
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static inline unsigned int evtchn_from_irq(int irq)
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{
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return irq_info[irq].evtchn;
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}
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static inline unsigned int index_from_irq(int irq)
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{
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return irq_info[irq].index;
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}
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static inline unsigned int type_from_irq(int irq)
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{
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return irq_info[irq].type;
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}
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static inline unsigned long active_evtchns(unsigned int cpu,
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struct shared_info *sh,
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unsigned int idx)
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{
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return (sh->evtchn_pending[idx] &
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cpu_evtchn_mask[cpu][idx] &
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~sh->evtchn_mask[idx]);
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}
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static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
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{
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int irq = evtchn_to_irq[chn];
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BUG_ON(irq == -1);
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#ifdef CONFIG_SMP
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irq_desc[irq].affinity = cpumask_of_cpu(cpu);
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#endif
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__clear_bit(chn, cpu_evtchn_mask[cpu_evtchn[chn]]);
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__set_bit(chn, cpu_evtchn_mask[cpu]);
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cpu_evtchn[chn] = cpu;
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}
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static void init_evtchn_cpu_bindings(void)
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{
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#ifdef CONFIG_SMP
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int i;
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/* By default all event channels notify CPU#0. */
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for (i = 0; i < NR_IRQS; i++)
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irq_desc[i].affinity = cpumask_of_cpu(0);
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#endif
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memset(cpu_evtchn, 0, sizeof(cpu_evtchn));
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memset(cpu_evtchn_mask[0], ~0, sizeof(cpu_evtchn_mask[0]));
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}
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static inline unsigned int cpu_from_evtchn(unsigned int evtchn)
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{
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return cpu_evtchn[evtchn];
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}
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static inline void clear_evtchn(int port)
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{
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struct shared_info *s = HYPERVISOR_shared_info;
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sync_clear_bit(port, &s->evtchn_pending[0]);
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}
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static inline void set_evtchn(int port)
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{
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struct shared_info *s = HYPERVISOR_shared_info;
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sync_set_bit(port, &s->evtchn_pending[0]);
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}
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/**
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* notify_remote_via_irq - send event to remote end of event channel via irq
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* @irq: irq of event channel to send event to
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*
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* Unlike notify_remote_via_evtchn(), this is safe to use across
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* save/restore. Notifications on a broken connection are silently
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* dropped.
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*/
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void notify_remote_via_irq(int irq)
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{
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int evtchn = evtchn_from_irq(irq);
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if (VALID_EVTCHN(evtchn))
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notify_remote_via_evtchn(evtchn);
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}
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EXPORT_SYMBOL_GPL(notify_remote_via_irq);
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static void mask_evtchn(int port)
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{
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struct shared_info *s = HYPERVISOR_shared_info;
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sync_set_bit(port, &s->evtchn_mask[0]);
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}
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static void unmask_evtchn(int port)
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{
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struct shared_info *s = HYPERVISOR_shared_info;
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unsigned int cpu = get_cpu();
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BUG_ON(!irqs_disabled());
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/* Slow path (hypercall) if this is a non-local port. */
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if (unlikely(cpu != cpu_from_evtchn(port))) {
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struct evtchn_unmask unmask = { .port = port };
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(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
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} else {
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struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
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sync_clear_bit(port, &s->evtchn_mask[0]);
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/*
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* The following is basically the equivalent of
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* 'hw_resend_irq'. Just like a real IO-APIC we 'lose
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* the interrupt edge' if the channel is masked.
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*/
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if (sync_test_bit(port, &s->evtchn_pending[0]) &&
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!sync_test_and_set_bit(port / BITS_PER_LONG,
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&vcpu_info->evtchn_pending_sel))
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vcpu_info->evtchn_upcall_pending = 1;
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}
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put_cpu();
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}
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static int find_unbound_irq(void)
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{
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int irq;
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/* Only allocate from dynirq range */
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for (irq = 0; irq < NR_IRQS; irq++)
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if (irq_bindcount[irq] == 0)
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break;
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if (irq == NR_IRQS)
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panic("No available IRQ to bind to: increase NR_IRQS!\n");
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return irq;
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}
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static int bind_evtchn_to_irq(unsigned int evtchn)
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{
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int irq;
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spin_lock(&irq_mapping_update_lock);
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irq = evtchn_to_irq[evtchn];
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if (irq == -1) {
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irq = find_unbound_irq();
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dynamic_irq_init(irq);
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set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
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handle_level_irq, "event");
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evtchn_to_irq[evtchn] = irq;
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irq_info[irq] = mk_irq_info(IRQT_EVTCHN, 0, evtchn);
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}
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irq_bindcount[irq]++;
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spin_unlock(&irq_mapping_update_lock);
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return irq;
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}
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static int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
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{
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struct evtchn_bind_virq bind_virq;
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int evtchn, irq;
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spin_lock(&irq_mapping_update_lock);
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irq = per_cpu(virq_to_irq, cpu)[virq];
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if (irq == -1) {
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bind_virq.virq = virq;
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bind_virq.vcpu = cpu;
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if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
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&bind_virq) != 0)
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BUG();
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evtchn = bind_virq.port;
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irq = find_unbound_irq();
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dynamic_irq_init(irq);
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set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
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handle_level_irq, "virq");
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evtchn_to_irq[evtchn] = irq;
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irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);
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per_cpu(virq_to_irq, cpu)[virq] = irq;
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bind_evtchn_to_cpu(evtchn, cpu);
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}
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irq_bindcount[irq]++;
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spin_unlock(&irq_mapping_update_lock);
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return irq;
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}
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static void unbind_from_irq(unsigned int irq)
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{
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struct evtchn_close close;
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int evtchn = evtchn_from_irq(irq);
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spin_lock(&irq_mapping_update_lock);
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if (VALID_EVTCHN(evtchn) && (--irq_bindcount[irq] == 0)) {
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close.port = evtchn;
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if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
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BUG();
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switch (type_from_irq(irq)) {
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case IRQT_VIRQ:
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per_cpu(virq_to_irq, cpu_from_evtchn(evtchn))
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[index_from_irq(irq)] = -1;
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break;
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default:
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break;
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}
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/* Closed ports are implicitly re-bound to VCPU0. */
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bind_evtchn_to_cpu(evtchn, 0);
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evtchn_to_irq[evtchn] = -1;
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irq_info[irq] = IRQ_UNBOUND;
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dynamic_irq_init(irq);
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}
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spin_unlock(&irq_mapping_update_lock);
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}
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int bind_evtchn_to_irqhandler(unsigned int evtchn,
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irqreturn_t (*handler)(int, void *),
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unsigned long irqflags,
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const char *devname, void *dev_id)
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{
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unsigned int irq;
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int retval;
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irq = bind_evtchn_to_irq(evtchn);
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retval = request_irq(irq, handler, irqflags, devname, dev_id);
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if (retval != 0) {
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unbind_from_irq(irq);
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return retval;
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}
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return irq;
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}
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EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler);
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int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
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irqreturn_t (*handler)(int, void *),
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unsigned long irqflags, const char *devname, void *dev_id)
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{
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unsigned int irq;
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int retval;
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irq = bind_virq_to_irq(virq, cpu);
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retval = request_irq(irq, handler, irqflags, devname, dev_id);
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if (retval != 0) {
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unbind_from_irq(irq);
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return retval;
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}
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return irq;
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}
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EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);
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void unbind_from_irqhandler(unsigned int irq, void *dev_id)
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{
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free_irq(irq, dev_id);
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unbind_from_irq(irq);
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}
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EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
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/*
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* Search the CPUs pending events bitmasks. For each one found, map
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* the event number to an irq, and feed it into do_IRQ() for
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* handling.
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*
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* Xen uses a two-level bitmap to speed searching. The first level is
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* a bitset of words which contain pending event bits. The second
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* level is a bitset of pending events themselves.
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*/
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fastcall void xen_evtchn_do_upcall(struct pt_regs *regs)
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{
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int cpu = get_cpu();
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struct shared_info *s = HYPERVISOR_shared_info;
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struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
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unsigned long pending_words;
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vcpu_info->evtchn_upcall_pending = 0;
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/* NB. No need for a barrier here -- XCHG is a barrier on x86. */
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pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
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while (pending_words != 0) {
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unsigned long pending_bits;
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int word_idx = __ffs(pending_words);
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pending_words &= ~(1UL << word_idx);
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while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
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int bit_idx = __ffs(pending_bits);
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int port = (word_idx * BITS_PER_LONG) + bit_idx;
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int irq = evtchn_to_irq[port];
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if (irq != -1) {
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regs->orig_eax = ~irq;
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do_IRQ(regs);
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}
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}
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}
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put_cpu();
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}
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/* Rebind an evtchn so that it gets delivered to a specific cpu */
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static void rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
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{
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struct evtchn_bind_vcpu bind_vcpu;
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int evtchn = evtchn_from_irq(irq);
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if (!VALID_EVTCHN(evtchn))
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return;
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/* Send future instances of this interrupt to other vcpu. */
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bind_vcpu.port = evtchn;
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bind_vcpu.vcpu = tcpu;
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/*
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* If this fails, it usually just indicates that we're dealing with a
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* virq or IPI channel, which don't actually need to be rebound. Ignore
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* it, but don't do the xenlinux-level rebind in that case.
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*/
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if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
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bind_evtchn_to_cpu(evtchn, tcpu);
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}
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static void set_affinity_irq(unsigned irq, cpumask_t dest)
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{
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unsigned tcpu = first_cpu(dest);
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rebind_irq_to_cpu(irq, tcpu);
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}
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static void enable_dynirq(unsigned int irq)
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{
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int evtchn = evtchn_from_irq(irq);
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if (VALID_EVTCHN(evtchn))
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unmask_evtchn(evtchn);
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}
|
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|
||||
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());
|
||||
}
|
||||
|
|
@ -0,0 +1,28 @@
|
|||
#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 */
|
||||
Loading…
Reference in New Issue