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 unsigned long xen_save_fl(void)
  23 {
  24         struct vcpu_info *vcpu;
  25         unsigned long flags;
  26
  27         vcpu = percpu_read(xen_vcpu);
  28
  29         /* flag has opposite sense of mask */
  30         flags = !vcpu->evtchn_upcall_mask;
  31
  32         /* convert to IF type flag
  33            -0 -> 0x00000000
  34            -1 -> 0xffffffff
  35         */
  36         return (-flags) & X86_EFLAGS_IF;
  37 }
  38 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  39
  40 static void xen_restore_fl(unsigned long flags)
  41 {
  42         struct vcpu_info *vcpu;
  43
  44         /* convert from IF type flag */
  45         flags = !(flags & X86_EFLAGS_IF);
  46
  47         /* There's a one instruction preempt window here.  We need to
  48            make sure we're don't switch CPUs between getting the vcpu
  49            pointer and updating the mask. */
  50         preempt_disable();
  51         vcpu = percpu_read(xen_vcpu);
  52         vcpu->evtchn_upcall_mask = flags;
  53         preempt_enable_no_resched();
  54
  55         /* Doesn't matter if we get preempted here, because any
  56            pending event will get dealt with anyway. */
  57
  58         if (flags == 0) {
  59                 preempt_check_resched();
  60                 barrier(); /* unmask then check (avoid races) */
  61                 if (unlikely(vcpu->evtchn_upcall_pending))
  62                         xen_force_evtchn_callback();
  63         }
  64 }
  65 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  66
  67 static void xen_irq_disable(void)
  68 {
  69         /* There's a one instruction preempt window here.  We need to
  70            make sure we're don't switch CPUs between getting the vcpu
  71            pointer and updating the mask. */
  72         preempt_disable();
  73         percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  74         preempt_enable_no_resched();
  75 }
  76 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  77
  78 static void xen_irq_enable(void)
  79 {
  80         struct vcpu_info *vcpu;
  81
  82         /* We don't need to worry about being preempted here, since
  83            either a) interrupts are disabled, so no preemption, or b)
  84            the caller is confused and is trying to re-enable interrupts
  85            on an indeterminate processor. */
  86
  87         vcpu = percpu_read(xen_vcpu);
  88         vcpu->evtchn_upcall_mask = 0;
  89
  90         /* Doesn't matter if we get preempted here, because any
  91            pending event will get dealt with anyway. */
  92
  93         barrier(); /* unmask then check (avoid races) */
  94         if (unlikely(vcpu->evtchn_upcall_pending))
  95                 xen_force_evtchn_callback();
  96 }
  97 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
  98
  99 static void xen_safe_halt(void)
 100 {
 101         /* Blocking includes an implicit local_irq_enable(). */
 102         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 103                 BUG();
 104 }
 105
 106 static void xen_halt(void)
 107 {
 108         if (irqs_disabled())
 109                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 110         else
 111                 xen_safe_halt();
 112 }
 113
 114 static const struct pv_irq_ops xen_irq_ops __initdata = {
 115         .init_IRQ = xen_init_IRQ,
 116
 117         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 118         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 119         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 120         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 121
 122         .safe_halt = xen_safe_halt,
 123         .halt = xen_halt,
 124 #ifdef CONFIG_X86_64
 125         .adjust_exception_frame = xen_adjust_exception_frame,
 126 #endif
 127 };
 128
 129 void __init xen_init_irq_ops()
 130 {
 131         pv_irq_ops = xen_irq_ops;
 132 }