hw/nvme: fix missing cq eventidx update

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>

diff --git a/hw/nvme/ctrl.c b/hw/nvme/ctrl.c
index 28e02ec7baa643414e3efeb12d10fe3bd3e4f2b9..226480033771f6d76d7c382e8526514e822d56ac 100644 (file)
--- a/hw/nvme/ctrl.c
+++ b/hw/nvme/ctrl.c
@@ -1334,6 +1334,15 @@ 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);
+
+    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;
@@ -1358,6 +1367,7 @@ static void nvme_post_cqes(void *opaque)
         hwaddr addr;
 
         if (n->dbbuf_enabled) {
+            nvme_update_cq_eventidx(cq);
             nvme_update_cq_head(cq);
         }