Re: [PATCH v2 03/17] hw/block/nvme: handle dma errors

[Keith Busch]

On Fri, Sep 18, 2020 at 10:36:07PM +0200, Klaus Jensen wrote:
> @@ -466,15 +476,21 @@ static void nvme_post_cqes(void *opaque)
>              break;
>          }
>  
> -        QTAILQ_REMOVE(&cq->req_list, req, entry);
>          sq = req->sq;
>          req->cqe.status = cpu_to_le16((req->status << 1) | cq->phase);
>          req->cqe.sq_id = cpu_to_le16(sq->sqid);
>          req->cqe.sq_head = cpu_to_le16(sq->head);
>          addr = cq->dma_addr + cq->tail * n->cqe_size;
> +        ret = pci_dma_write(&n->parent_obj, addr, (void *)&req->cqe,
> +                            sizeof(req->cqe));
> +        if (ret) {
> +            trace_pci_nvme_err_addr_write(addr);
> +            timer_mod(cq->timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
> +                      500 * SCALE_MS);
> +            break;
> +        }
> +        QTAILQ_REMOVE(&cq->req_list, req, entry);

Is this error really ever transient such that a retry later may be
successful? I didn't find a way that appeared that it could be. If not,
this probably deserves a CFS condition rather than a retry.