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         /* There's a one instruction preempt window here.  We need to
  51            make sure we're don't switch CPUs between getting the vcpu
  52            pointer and updating the mask. */
  53         preempt_disable();
  54         vcpu = this_cpu_read(xen_vcpu);
  55         vcpu->evtchn_upcall_mask = flags;
  56         preempt_enable_no_resched();
  57
  58         /* Doesn't matter if we get preempted here, because any
  59            pending event will get dealt with anyway. */
  60
  61         if (flags == 0) {
  62                 preempt_check_resched();
  63                 barrier(); /* unmask then check (avoid races) */
  64                 if (unlikely(vcpu->evtchn_upcall_pending))
  65                         xen_force_evtchn_callback();
  66         }
  67 }
  68 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  69
  70 static void xen_irq_disable(void)
  71 {
  72         /* There's a one instruction preempt window here.  We need to
  73            make sure we're don't switch CPUs between getting the vcpu
  74            pointer and updating the mask. */
  75         preempt_disable();
  76         this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  77         preempt_enable_no_resched();
  78 }
  79 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  80
  81 static void xen_irq_enable(void)
  82 {
  83         struct vcpu_info *vcpu;
  84
  85         /* We don't need to worry about being preempted here, since
  86            either a) interrupts are disabled, so no preemption, or b)
  87            the caller is confused and is trying to re-enable interrupts
  88            on an indeterminate processor. */
  89
  90         vcpu = this_cpu_read(xen_vcpu);
  91         vcpu->evtchn_upcall_mask = 0;
  92
  93         /* Doesn't matter if we get preempted here, because any
  94            pending event will get dealt with anyway. */
  95
  96         barrier(); /* unmask then check (avoid races) */
  97         if (unlikely(vcpu->evtchn_upcall_pending))
  98                 xen_force_evtchn_callback();
  99 }
 100 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 101
 102 static void xen_safe_halt(void)
 103 {
 104         /* Blocking includes an implicit local_irq_enable(). */
 105         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 106                 BUG();
 107 }
 108
 109 static void xen_halt(void)
 110 {
 111         if (irqs_disabled())
 112                 HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 113         else
 114                 xen_safe_halt();
 115 }
 116
 117 static const struct pv_irq_ops xen_irq_ops __initconst = {
 118         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 119         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 120         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 121         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 122
 123         .safe_halt = xen_safe_halt,
 124         .halt = xen_halt,
 125 #ifdef CONFIG_X86_64
 126         .adjust_exception_frame = xen_adjust_exception_frame,
 127 #endif
 128 };
 129
 130 void __init xen_init_irq_ops(void)
 131 {
 132         pv_irq_ops = xen_irq_ops;
 133         x86_init.irqs.intr_init = xen_init_IRQ;
 134 }