arch/x86/xen/irq.c

   1 #include <linux/hardirq.h>
   2
   3 #include <asm/x86_init.h>
   4
   5 #include <xen/interface/xen.h>
   6 #include <xen/interface/sched.h>
   7 #include <xen/interface/vcpu.h>
   8 #include <xen/events.h>
   9
  10 #include <asm/xen/hypercall.h>
  11 #include <asm/xen/hypervisor.h>
  12
  13 #include "xen-ops.h"
  14
  15 /*
  16  * Force a proper event-channel callback from Xen after clearing the
  17  * callback mask. We do this in a very simple manner, by making a call
  18  * down into Xen. The pending flag will be checked by Xen on return.
  19  */
  20 void xen_force_evtchn_callback(void)
  21 {
  22         (void)HYPERVISOR_xen_version(0, NULL);
  23 }
  24
  25 static unsigned long xen_save_fl(void)
  26 {
  27         struct vcpu_info *vcpu;
  28         unsigned long flags;
  29
  30         vcpu = this_cpu_read(xen_vcpu);
  31
  32         /* flag has opposite sense of mask */
  33         flags = !vcpu->evtchn_upcall_mask;
  34
  35         /* convert to IF type flag
  36            -0 -> 0x00000000
  37            -1 -> 0xffffffff
  38         */
  39         return (-flags) & X86_EFLAGS_IF;
  40 }
  41 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  42
  43 static void xen_restore_fl(unsigned long flags)
  44 {
  45         struct vcpu_info *vcpu;
  46
  47         /* convert from IF type flag */
  48         flags = !(flags & X86_EFLAGS_IF);
  49
  50         /* See xen_irq_enable() for why preemption must be disabled. */
  51         preempt_disable();
  52         vcpu = this_cpu_read(xen_vcpu);
  53         vcpu->evtchn_upcall_mask = flags;
  54
  55         if (flags == 0) {
  56                 barrier(); /* unmask then check (avoid races) */
  57                 if (unlikely(vcpu->evtchn_upcall_pending))
  58                         xen_force_evtchn_callback();
  59                 preempt_enable();
  60         } else
  61                 preempt_enable_no_resched();
  62 }
  63 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  64
  65 static void xen_irq_disable(void)
  66 {
  67         /* There's a one instruction preempt window here.  We need to
  68            make sure we're don't switch CPUs between getting the vcpu
  69            pointer and updating the mask. */
  70         preempt_disable();
  71         this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  72         preempt_enable_no_resched();
  73 }
  74 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  75
  76 static void xen_irq_enable(void)
  77 {
  78         struct vcpu_info *vcpu;
  79
  80         /*
  81          * We may be preempted as soon as vcpu->evtchn_upcall_mask is
  82          * cleared, so disable preemption to ensure we check for
  83          * events on the VCPU we are still running on.
  84          */
  85         preempt_disable();
  86
  87         vcpu = this_cpu_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         preempt_enable();
  98 }
  99 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 100
 101 static void xen_safe_halt(void)
 102 {
 103         /* Blocking includes an implicit local_irq_enable(). */
 104         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 105                 BUG();
 106 }
 107
 108 static void xen_halt(void)
 109 {
 110         if (irqs_disabled())
 111                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 112         else
 113                 xen_safe_halt();
 114 }
 115
 116 static const struct pv_irq_ops xen_irq_ops __initconst = {
 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(void)
 130 {
 131         pv_irq_ops = xen_irq_ops;
 132         x86_init.irqs.intr_init = xen_init_IRQ;
 133 }