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 #ifdef CONFIG_X86_64
  25         int i;
  26
  27         /* Create identity vector->irq map */
  28         for(i = 0; i < NR_VECTORS; i++) {
  29                 int cpu;
  30
  31                 for_each_possible_cpu(cpu)
  32                         per_cpu(vector_irq, cpu)[i] = i;
  33         }
  34 #endif  /* CONFIG_X86_64 */
  35
  36         xen_init_IRQ();
  37 }
  38
  39 static unsigned long xen_save_fl(void)
  40 {
  41         struct vcpu_info *vcpu;
  42         unsigned long flags;
  43
  44         vcpu = x86_read_percpu(xen_vcpu);
  45
  46         /* flag has opposite sense of mask */
  47         flags = !vcpu->evtchn_upcall_mask;
  48
  49         /* convert to IF type flag
  50            -0 -> 0x00000000
  51            -1 -> 0xffffffff
  52         */
  53         return (-flags) & X86_EFLAGS_IF;
  54 }
  55
  56 static void xen_restore_fl(unsigned long flags)
  57 {
  58         struct vcpu_info *vcpu;
  59
  60         /* convert from IF type flag */
  61         flags = !(flags & X86_EFLAGS_IF);
  62
  63         /* There's a one instruction preempt window here.  We need to
  64            make sure we're don't switch CPUs between getting the vcpu
  65            pointer and updating the mask. */
  66         preempt_disable();
  67         vcpu = x86_read_percpu(xen_vcpu);
  68         vcpu->evtchn_upcall_mask = flags;
  69         preempt_enable_no_resched();
  70
  71         /* Doesn't matter if we get preempted here, because any
  72            pending event will get dealt with anyway. */
  73
  74         if (flags == 0) {
  75                 preempt_check_resched();
  76                 barrier(); /* unmask then check (avoid races) */
  77                 if (unlikely(vcpu->evtchn_upcall_pending))
  78                         xen_force_evtchn_callback();
  79         }
  80 }
  81
  82 static void xen_irq_disable(void)
  83 {
  84         /* There's a one instruction preempt window here.  We need to
  85            make sure we're don't switch CPUs between getting the vcpu
  86            pointer and updating the mask. */
  87         preempt_disable();
  88         x86_read_percpu(xen_vcpu)->evtchn_upcall_mask = 1;
  89         preempt_enable_no_resched();
  90 }
  91
  92 static void xen_irq_enable(void)
  93 {
  94         struct vcpu_info *vcpu;
  95
  96         /* We don't need to worry about being preempted here, since
  97            either a) interrupts are disabled, so no preemption, or b)
  98            the caller is confused and is trying to re-enable interrupts
  99            on an indeterminate processor. */
 100
 101         vcpu = x86_read_percpu(xen_vcpu);
 102         vcpu->evtchn_upcall_mask = 0;
 103
 104         /* Doesn't matter if we get preempted here, because any
 105            pending event will get dealt with anyway. */
 106
 107         barrier(); /* unmask then check (avoid races) */
 108         if (unlikely(vcpu->evtchn_upcall_pending))
 109                 xen_force_evtchn_callback();
 110 }
 111
 112 static void xen_safe_halt(void)
 113 {
 114         /* Blocking includes an implicit local_irq_enable(). */
 115         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 116                 BUG();
 117 }
 118
 119 static void xen_halt(void)
 120 {
 121         if (irqs_disabled())
 122                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 123         else
 124                 xen_safe_halt();
 125 }
 126
 127 static const struct pv_irq_ops xen_irq_ops __initdata = {
 128         .init_IRQ = __xen_init_IRQ,
 129         .save_fl = xen_save_fl,
 130         .restore_fl = xen_restore_fl,
 131         .irq_disable = xen_irq_disable,
 132         .irq_enable = xen_irq_enable,
 133         .safe_halt = xen_safe_halt,
 134         .halt = xen_halt,
 135 #ifdef CONFIG_X86_64
 136         .adjust_exception_frame = xen_adjust_exception_frame,
 137 #endif
 138 };
 139
 140 void __init xen_init_irq_ops()
 141 {
 142         pv_irq_ops = xen_irq_ops;
 143 }