kvm: avoid reentring kvm_flush_coalesced_mmio_buffer()

mmio callbacks invoked by kvm_flush_coalesced_mmio_buffer() may
themselves indirectly call kvm_flush_coalesced_mmio_buffer().
Prevent reentering the function by checking a flag that indicates
we're processing coalesced mmio requests.

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/kvm-all.c b/kvm-all.c
index e7faf5cba9..c09ddf7ac5 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -64,6 +64,7 @@ struct KVMState
     int vmfd;
     int coalesced_mmio;
     struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
+    bool coalesced_flush_in_progress;
     int broken_set_mem_region;
     int migration_log;
     int vcpu_events;
@@ -876,6 +877,13 @@ static int kvm_handle_internal_error(CPUState *env, struct kvm_run *run)
 void kvm_flush_coalesced_mmio_buffer(void)
 {
     KVMState *s = kvm_state;
+
+    if (s->coalesced_flush_in_progress) {
+        return;
+    }
+
+    s->coalesced_flush_in_progress = true;
+
     if (s->coalesced_mmio_ring) {
         struct kvm_coalesced_mmio_ring *ring = s->coalesced_mmio_ring;
         while (ring->first != ring->last) {
@@ -888,6 +896,8 @@ void kvm_flush_coalesced_mmio_buffer(void)
             ring->first = (ring->first + 1) % KVM_COALESCED_MMIO_MAX;
         }
     }
+
+    s->coalesced_flush_in_progress = false;
 }
 
 static void do_kvm_cpu_synchronize_state(void *_env)