arch/x86/xen/irq.c

   1 #include <linux/hardirq.h>
   2
   3 #include <xen/interface/xen.h>
   4 #include <xen/interface/sched.h>
   5 #include <xen/interface/vcpu.h>
   6
   7 #include <asm/xen/hypercall.h>
   8 #include <asm/xen/hypervisor.h>
   9
  10 #include "xen-ops.h"
  11
  12 /*
  13  * Force a proper event-channel callback from Xen after clearing the
  14  * callback mask. We do this in a very simple manner, by making a call
  15  * down into Xen. The pending flag will be checked by Xen on return.
  16  */
  17 void xen_force_evtchn_callback(void)
  18 {
  19         (void)HYPERVISOR_xen_version(0, NULL);
  20 }
  21
  22 static void __init __xen_init_IRQ(void)
  23 {
  24         int i;
  25
  26         /* Create identity vector->irq map */
  27         for(i = 0; i < NR_VECTORS; i++) {
  28                 int cpu;
  29
  30                 for_each_possible_cpu(cpu)
  31                         per_cpu(vector_irq, cpu)[i] = i;
  32         }
  33
  34         xen_init_IRQ();
  35 }
  36
  37 static unsigned long xen_save_fl(void)
  38 {
  39         struct vcpu_info *vcpu;
  40         unsigned long flags;
  41
  42         vcpu = x86_read_percpu(xen_vcpu);
  43
  44         /* flag has opposite sense of mask */
  45         flags = !vcpu->evtchn_upcall_mask;
  46
  47         /* convert to IF type flag
  48            -0 -> 0x00000000
  49            -1 -> 0xffffffff
  50         */
  51         return (-flags) & X86_EFLAGS_IF;
  52 }
  53
  54 static void xen_restore_fl(unsigned long flags)
  55 {
  56         struct vcpu_info *vcpu;
  57
  58         /* convert from IF type flag */
  59         flags = !(flags & X86_EFLAGS_IF);
  60
  61         /* There's a one instruction preempt window here.  We need to
  62            make sure we're don't switch CPUs between getting the vcpu
  63            pointer and updating the mask. */
  64         preempt_disable();
  65         vcpu = x86_read_percpu(xen_vcpu);
  66         vcpu->evtchn_upcall_mask = flags;
  67         preempt_enable_no_resched();
  68
  69         /* Doesn't matter if we get preempted here, because any
  70            pending event will get dealt with anyway. */
  71
  72         if (flags == 0) {
  73                 preempt_check_resched();
  74                 barrier(); /* unmask then check (avoid races) */
  75                 if (unlikely(vcpu->evtchn_upcall_pending))
  76                         xen_force_evtchn_callback();
  77         }
  78 }
  79
  80 static void xen_irq_disable(void)
  81 {
  82         /* There's a one instruction preempt window here.  We need to
  83            make sure we're don't switch CPUs between getting the vcpu
  84            pointer and updating the mask. */
  85         preempt_disable();
  86         x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
  87         preempt_enable_no_resched();
  88 }
  89
  90 static void xen_irq_enable(void)
  91 {
  92         struct vcpu_info *vcpu;
  93
  94         /* We don't need to worry about being preempted here, since
  95            either a) interrupts are disabled, so no preemption, or b)
  96            the caller is confused and is trying to re-enable interrupts
  97            on an indeterminate processor. */
  98
  99         vcpu = x86_read_percpu(xen_vcpu);
 100         vcpu->evtchn_upcall_mask = 0;
 101
 102         /* Doesn't matter if we get preempted here, because any
 103            pending event will get dealt with anyway. */
 104
 105         barrier(); /* unmask then check (avoid races) */
 106         if (unlikely(vcpu->evtchn_upcall_pending))
 107                 xen_force_evtchn_callback();
 108 }
 109
 110 static void xen_safe_halt(void)
 111 {
 112         /* Blocking includes an implicit local_irq_enable(). */
 113         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 114                 BUG();
 115 }
 116
 117 static void xen_halt(void)
 118 {
 119         if (irqs_disabled())
 120                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 121         else
 122                 xen_safe_halt();
 123 }
 124
 125 static const struct pv_irq_ops xen_irq_ops __initdata = {
 126         .init_IRQ = __xen_init_IRQ,
 127         .save_fl = xen_save_fl,
 128         .restore_fl = xen_restore_fl,
 129         .irq_disable = xen_irq_disable,
 130         .irq_enable = xen_irq_enable,
 131         .safe_halt = xen_safe_halt,
 132         .halt = xen_halt,
 133 #ifdef CONFIG_X86_64
 134         .adjust_exception_frame = xen_adjust_exception_frame,
 135 #endif
 136 };
 137
 138 void __init xen_init_irq_ops()
 139 {
 140         pv_irq_ops = xen_irq_ops;
 141 }