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 = percpu_read(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 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  54
  55 static void xen_restore_fl(unsigned long flags)
  56 {
  57         struct vcpu_info *vcpu;
  58
  59         /* convert from IF type flag */
  60         flags = !(flags & X86_EFLAGS_IF);
  61
  62         /* There's a one instruction preempt window here.  We need to
  63            make sure we're don't switch CPUs between getting the vcpu
  64            pointer and updating the mask. */
  65         preempt_disable();
  66         vcpu = percpu_read(xen_vcpu);
  67         vcpu->evtchn_upcall_mask = flags;
  68         preempt_enable_no_resched();
  69
  70         /* Doesn't matter if we get preempted here, because any
  71            pending event will get dealt with anyway. */
  72
  73         if (flags == 0) {
  74                 preempt_check_resched();
  75                 barrier(); /* unmask then check (avoid races) */
  76                 if (unlikely(vcpu->evtchn_upcall_pending))
  77                         xen_force_evtchn_callback();
  78         }
  79 }
  80 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  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         percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  89         preempt_enable_no_resched();
  90 }
  91 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  92
  93 static void xen_irq_enable(void)
  94 {
  95         struct vcpu_info *vcpu;
  96
  97         /* We don't need to worry about being preempted here, since
  98            either a) interrupts are disabled, so no preemption, or b)
  99            the caller is confused and is trying to re-enable interrupts
 100            on an indeterminate processor. */
 101
 102         vcpu = percpu_read(xen_vcpu);
 103         vcpu->evtchn_upcall_mask = 0;
 104
 105         /* Doesn't matter if we get preempted here, because any
 106            pending event will get dealt with anyway. */
 107
 108         barrier(); /* unmask then check (avoid races) */
 109         if (unlikely(vcpu->evtchn_upcall_pending))
 110                 xen_force_evtchn_callback();
 111 }
 112 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 113
 114 static void xen_safe_halt(void)
 115 {
 116         /* Blocking includes an implicit local_irq_enable(). */
 117         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 118                 BUG();
 119 }
 120
 121 static void xen_halt(void)
 122 {
 123         if (irqs_disabled())
 124                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 125         else
 126                 xen_safe_halt();
 127 }
 128
 129 static const struct pv_irq_ops xen_irq_ops __initdata = {
 130         .init_IRQ = __xen_init_IRQ,
 131
 132         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 133         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 134         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 135         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 136
 137         .safe_halt = xen_safe_halt,
 138         .halt = xen_halt,
 139 #ifdef CONFIG_X86_64
 140         .adjust_exception_frame = xen_adjust_exception_frame,
 141 #endif
 142 };
 143
 144 void __init xen_init_irq_ops()
 145 {
 146         pv_irq_ops = xen_irq_ops;
 147 }