1 files changed, 30 insertions, 16 deletions

diff --git a/arch/x86/xen/events.c b/arch/x86/xen/events.c
index f73b53bd65b7..85bac298b3cb 100644
--- a/arch/x86/xen/events.c
+++ b/arch/x86/xen/events.c
@@ -517,29 +517,43 @@ void xen_evtchn_do_upcall(struct pt_regs *regs)
         int cpu = get_cpu();
         struct shared_info *s = HYPERVISOR_shared_info;
         struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
-        unsigned long pending_words;
+        static DEFINE_PER_CPU(unsigned, nesting_count);
+        unsigned count;
 
-        vcpu_info->evtchn_upcall_pending = 0;
+        do {
+                unsigned long pending_words;
 
-        /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
-        pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
-        while (pending_words != 0) {
-                unsigned long pending_bits;
-                int word_idx = __ffs(pending_words);
-                pending_words &= ~(1UL << word_idx);
+                vcpu_info->evtchn_upcall_pending = 0;
 
-                while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
-                        int bit_idx = __ffs(pending_bits);
-                        int port = (word_idx * BITS_PER_LONG) + bit_idx;
-                        int irq = evtchn_to_irq[port];
+                if (__get_cpu_var(nesting_count)++)
+                        goto out;
 
-                        if (irq != -1) {
-                                regs->orig_ax = ~irq;
-                                do_IRQ(regs);
+                /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
+                pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
+                while (pending_words != 0) {
+                        unsigned long pending_bits;
+                        int word_idx = __ffs(pending_words);
+                        pending_words &= ~(1UL << word_idx);
+
+                        while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
+                                int bit_idx = __ffs(pending_bits);
+                                int port = (word_idx * BITS_PER_LONG) + bit_idx;
+                                int irq = evtchn_to_irq[port];
+
+                                if (irq != -1) {
+                                        regs->orig_ax = ~irq;
+                                        do_IRQ(regs);
+                                }
                         }
                 }
-        }
 
+                BUG_ON(!irqs_disabled());
+
+                count = __get_cpu_var(nesting_count);
+                __get_cpu_var(nesting_count) = 0;
+        } while(count != 1);
+
+out:
         put_cpu();
 }