[PATCH 10/47] hw/nvme: fix missing cq eventidx update

[Michael Tokarev]

From: Klaus Jensen <k.jensen@samsung.com>

Prior to reading the shadow doorbell cq head, we have to update the
eventidx. Otherwise, we risk that the driver will skip an mmio doorbell
write. This happens on riscv64, as reported by Guenter.

Adding the missing update to the cq eventidx fixes the issue.

Fixes: 3f7fe8de3d49 ("hw/nvme: Implement shadow doorbell buffer support")
Cc: qemu-stable@nongnu.org
Cc: qemu-riscv@nongnu.org
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
(cherry picked from commit fa5db2aa168bdc0f15c269b6212ef47632fab8ba)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 hw/nvme/ctrl.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 83f5e58e8d..366b973a9e 100644
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -1331,6 +1331,15 @@ static inline void nvme_blk_write(BlockBackend *blk, 
int64_t offset,
     }
 }
 
+static void nvme_update_cq_eventidx(const NvmeCQueue *cq)
+{
+    uint32_t v = cpu_to_le32(cq->head);
+
+    //not in 7.2: trace_pci_nvme_update_cq_eventidx(cq->cqid, cq->head);
+
+    pci_dma_write(PCI_DEVICE(cq->ctrl), cq->ei_addr, &v, sizeof(v));
+}
+
 static void nvme_update_cq_head(NvmeCQueue *cq)
 {
     uint32_t v;
@@ -1355,6 +1364,7 @@ static void nvme_post_cqes(void *opaque)
         hwaddr addr;
 
         if (n->dbbuf_enabled) {
+            nvme_update_cq_eventidx(cq);
             nvme_update_cq_head(cq);
         }
 
-- 
2.30.2