[Qemu-devel] [PATCH] nvme: Fix spurious interrupts

[Keith Busch <keith.busch@intel.com>]

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>
---
 hw/block/nvme.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 9fbe5673cb..7c8c63e8f5 100644
--- 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)
-- 
2.14.4