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[Qemu-devel] [PATCH 5/5] nvme: Missing MSI message upon partial CQ read

From: Shimi Gersner
Subject: [Qemu-devel] [PATCH 5/5] nvme: Missing MSI message upon partial CQ read
Date: Fri, 22 Jun 2018 11:22:37 +0000

When MSIx interrupts are enabled, each CQ is associated with
a vector which is expected to be called upon ready data
in the CQ buffer. After guest reads from the buffer, it updates
the processed buffer position using a CQ dedicated DB.

Upon reading only partial data from the CQ buffer, device
fails to re-send a new MSI message stating buffer still has
unread data. The fix ensures a new message will be sent.

Change-Id: I10190be127b8dcbd89732cfb95ea37faf8c5779b
Signed-off-by: Shimi Gersner <address@hidden>
 hw/block/nvme.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index f639d7ae73..e2dca6e57f 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -1152,8 +1152,12 @@ static void nvme_process_db(NvmeCtrl *n, hwaddr addr, 
int val)
+        // When we have more messages, we should make sure irq is asserted. 
When MSIx is used
+        // this will make sure another notification is sent to the guest.
         if (cq->tail == cq->head) {
             nvme_irq_deassert(n, cq);
+        } else {
+            nvme_irq_assert(n, cq);
     } else {
         /* Submission queue doorbell write */

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