nvme: Fix spurious interrupts

The code had asserted an interrupt every time it was requested to check
for new completion queue entries.This can result in spurious interrupts
seen by the guest OS.

Fix this by asserting an interrupt only if there are un-acknowledged
completion queue entries available.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 9fbe567..7c8c63e 100644 (file)
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -272,7 +272,9 @@ static void nvme_post_cqes(void *opaque)
             sizeof(req->cqe));
         QTAILQ_INSERT_TAIL(&sq->req_list, req, entry);
     }
-    nvme_irq_assert(n, cq);
+    if (cq->tail != cq->head) {
+        nvme_irq_assert(n, cq);
+    }
 }
 
 static void nvme_enqueue_req_completion(NvmeCQueue *cq, NvmeRequest *req)