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/features.h>
   9 #include <xen/events.h>
  10
  11 #include <asm/xen/hypercall.h>
  12 #include <asm/xen/hypervisor.h>
  13
  14 #include "xen-ops.h"
  15
  16 /*
  17  * Force a proper event-channel callback from Xen after clearing the
  18  * callback mask. We do this in a very simple manner, by making a call
  19  * down into Xen. The pending flag will be checked by Xen on return.
  20  */
  21 void xen_force_evtchn_callback(void)
  22 {
  23         (void)HYPERVISOR_xen_version(0, NULL);
  24 }
  25
  26 asmlinkage __visible unsigned long xen_save_fl(void)
  27 {
  28         struct vcpu_info *vcpu;
  29         unsigned long flags;
  30
  31         vcpu = this_cpu_read(xen_vcpu);
  32
  33         /* flag has opposite sense of mask */
  34         flags = !vcpu->evtchn_upcall_mask;
  35
  36         /* convert to IF type flag
  37            -0 -> 0x00000000
  38            -1 -> 0xffffffff
  39         */
  40         return (-flags) & X86_EFLAGS_IF;
  41 }
  42 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  43
  44 __visible void xen_restore_fl(unsigned long flags)
  45 {
  46         struct vcpu_info *vcpu;
  47
  48         /* convert from IF type flag */
  49         flags = !(flags & X86_EFLAGS_IF);
  50
  51         /* See xen_irq_enable() for why preemption must be disabled. */
  52         preempt_disable();
  53         vcpu = this_cpu_read(xen_vcpu);
  54         vcpu->evtchn_upcall_mask = flags;
  55
  56         if (flags == 0) {
  57                 barrier(); /* unmask then check (avoid races) */
  58                 if (unlikely(vcpu->evtchn_upcall_pending))
  59                         xen_force_evtchn_callback();
  60                 preempt_enable();
  61         } else
  62                 preempt_enable_no_resched();
  63 }
  64 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  65
  66 asmlinkage __visible void xen_irq_disable(void)
  67 {
  68         /* There's a one instruction preempt window here.  We need to
  69            make sure we're don't switch CPUs between getting the vcpu
  70            pointer and updating the mask. */
  71         preempt_disable();
  72         this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  73         preempt_enable_no_resched();
  74 }
  75 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  76
  77 asmlinkage __visible void xen_irq_enable(void)
  78 {
  79         struct vcpu_info *vcpu;
  80
  81         /*
  82          * We may be preempted as soon as vcpu->evtchn_upcall_mask is
  83          * cleared, so disable preemption to ensure we check for
  84          * events on the VCPU we are still running on.
  85          */
  86         preempt_disable();
  87
  88         vcpu = this_cpu_read(xen_vcpu);
  89         vcpu->evtchn_upcall_mask = 0;
  90
  91         /* Doesn't matter if we get preempted here, because any
  92            pending event will get dealt with anyway. */
  93
  94         barrier(); /* unmask then check (avoid races) */
  95         if (unlikely(vcpu->evtchn_upcall_pending))
  96                 xen_force_evtchn_callback();
  97
  98         preempt_enable();
  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,
 113                                    xen_vcpu_nr(smp_processor_id()), NULL);
 114         else
 115                 xen_safe_halt();
 116 }
 117
 118 static const struct pv_irq_ops xen_irq_ops __initconst = {
 119         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 120         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 121         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 122         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 123
 124         .safe_halt = xen_safe_halt,
 125         .halt = xen_halt,
 126 };
 127
 128 void __init xen_init_irq_ops(void)
 129 {
 130         /* For PVH we use default pv_irq_ops settings. */
 131         if (!xen_feature(XENFEAT_hvm_callback_vector))
 132                 pv_irq_ops = xen_irq_ops;
 133         x86_init.irqs.intr_init = xen_init_IRQ;
 134 }