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
   9 #include <asm/xen/hypercall.h>
  10 #include <asm/xen/hypervisor.h>
  11
  12 #include "xen-ops.h"
  13
  14 /*
  15  * Force a proper event-channel callback from Xen after clearing the
  16  * callback mask. We do this in a very simple manner, by making a call
  17  * down into Xen. The pending flag will be checked by Xen on return.
  18  */
  19 void xen_force_evtchn_callback(void)
  20 {
  21         (void)HYPERVISOR_xen_version(0, NULL);
  22 }
  23
  24 static unsigned long xen_save_fl(void)
  25 {
  26         struct vcpu_info *vcpu;
  27         unsigned long flags;
  28
  29         vcpu = percpu_read(xen_vcpu);
  30
  31         /* flag has opposite sense of mask */
  32         flags = !vcpu->evtchn_upcall_mask;
  33
  34         /* convert to IF type flag
  35            -0 -> 0x00000000
  36            -1 -> 0xffffffff
  37         */
  38         return (-flags) & X86_EFLAGS_IF;
  39 }
  40 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  41
  42 static void xen_restore_fl(unsigned long flags)
  43 {
  44         struct vcpu_info *vcpu;
  45
  46         /* convert from IF type flag */
  47         flags = !(flags & X86_EFLAGS_IF);
  48
  49         /* There's a one instruction preempt window here.  We need to
  50            make sure we're don't switch CPUs between getting the vcpu
  51            pointer and updating the mask. */
  52         preempt_disable();
  53         vcpu = percpu_read(xen_vcpu);
  54         vcpu->evtchn_upcall_mask = flags;
  55         preempt_enable_no_resched();
  56
  57         /* Doesn't matter if we get preempted here, because any
  58            pending event will get dealt with anyway. */
  59
  60         if (flags == 0) {
  61                 preempt_check_resched();
  62                 barrier(); /* unmask then check (avoid races) */
  63                 if (unlikely(vcpu->evtchn_upcall_pending))
  64                         xen_force_evtchn_callback();
  65         }
  66 }
  67 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  68
  69 static void xen_irq_disable(void)
  70 {
  71         /* There's a one instruction preempt window here.  We need to
  72            make sure we're don't switch CPUs between getting the vcpu
  73            pointer and updating the mask. */
  74         preempt_disable();
  75         percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  76         preempt_enable_no_resched();
  77 }
  78 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  79
  80 static void xen_irq_enable(void)
  81 {
  82         struct vcpu_info *vcpu;
  83
  84         /* We don't need to worry about being preempted here, since
  85            either a) interrupts are disabled, so no preemption, or b)
  86            the caller is confused and is trying to re-enable interrupts
  87            on an indeterminate processor. */
  88
  89         vcpu = percpu_read(xen_vcpu);
  90         vcpu->evtchn_upcall_mask = 0;
  91
  92         /* Doesn't matter if we get preempted here, because any
  93            pending event will get dealt with anyway. */
  94
  95         barrier(); /* unmask then check (avoid races) */
  96         if (unlikely(vcpu->evtchn_upcall_pending))
  97                 xen_force_evtchn_callback();
  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 __initdata = {
 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         x86_init.irqs.intr_init = xen_init_IRQ;
 133 }