Re: [PATCH v2 06/11] util/vfio-helpers: Pass Error handle to qemu_vfio_dma_map()

[Klaus Jensen <its@irrelevant.dk>]

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On Aug 26 21:50, Philippe Mathieu-Daudé wrote:
> Currently qemu_vfio_dma_map() displays errors on stderr.
> When using management interface, this information is simply
> lost. Pass qemu_vfio_dma_map() an Error** handle so it can
> propagate the error to callers.
> 
> Reviewed-by: Fam Zheng <fam@euphon.net>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/qemu/vfio-helpers.h |  2 +-
>  block/nvme.c                | 22 +++++++++++-----------
>  util/vfio-helpers.c         | 10 ++++++----
>  3 files changed, 18 insertions(+), 16 deletions(-)
> 
> diff --git a/include/qemu/vfio-helpers.h b/include/qemu/vfio-helpers.h
> index 4491c8e1a6e..bde9495b254 100644
> --- a/include/qemu/vfio-helpers.h
> +++ b/include/qemu/vfio-helpers.h
> @@ -18,7 +18,7 @@ typedef struct QEMUVFIOState QEMUVFIOState;
>  QEMUVFIOState *qemu_vfio_open_pci(const char *device, Error **errp);
>  void qemu_vfio_close(QEMUVFIOState *s);
>  int qemu_vfio_dma_map(QEMUVFIOState *s, void *host, size_t size,
> -                      bool temporary, uint64_t *iova_list);
> +                      bool temporary, uint64_t *iova_list, Error **errp);
>  int qemu_vfio_dma_reset_temporary(QEMUVFIOState *s);
>  void qemu_vfio_dma_unmap(QEMUVFIOState *s, void *host);
>  void *qemu_vfio_pci_map_bar(QEMUVFIOState *s, int index,
> diff --git a/block/nvme.c b/block/nvme.c
> index 0786c501e46..80546b0babd 100644
> --- a/block/nvme.c
> +++ b/block/nvme.c
> @@ -176,12 +176,11 @@ static bool nvme_init_queue(BDRVNVMeState *s, NVMeQueue *q,
>          return false;
>      }
>      memset(q->queue, 0, bytes);
> -    r = qemu_vfio_dma_map(s->vfio, q->queue, bytes, false, &q->iova);
> +    r = qemu_vfio_dma_map(s->vfio, q->queue, bytes, false, &q->iova, errp);
>      if (r) {
> -        error_setg(errp, "Cannot map queue");
> -        return false;
> +        error_prepend(errp, "Cannot map queue: ");
>      }
> -    return true;
> +    return r == 0;
>  }
>  
>  static void nvme_free_queue_pair(NVMeQueuePair *q)
> @@ -239,9 +238,9 @@ static NVMeQueuePair *nvme_create_queue_pair(BDRVNVMeState *s,
>      qemu_co_queue_init(&q->free_req_queue);
>      q->completion_bh = aio_bh_new(aio_context, nvme_process_completion_bh, q);
>      r = qemu_vfio_dma_map(s->vfio, q->prp_list_pages, bytes,
> -                          false, &prp_list_iova);
> +                          false, &prp_list_iova, errp);
>      if (r) {
> -        error_setg_errno(errp, -r, "Cannot map buffer for DMA");
> +        error_prepend(errp, "Cannot map buffer for DMA: ");
>          goto fail;
>      }
>      q->free_req_head = -1;
> @@ -534,9 +533,9 @@ static bool nvme_identify(BlockDriverState *bs, int namespace, Error **errp)
>          error_setg(errp, "Cannot allocate buffer for identify response");
>          goto out;
>      }
> -    r = qemu_vfio_dma_map(s->vfio, id, id_size, true, &iova);
> +    r = qemu_vfio_dma_map(s->vfio, id, id_size, true, &iova, errp);
>      if (r) {
> -        error_setg(errp, "Cannot map buffer for DMA");
> +        error_prepend(errp, "Cannot map buffer for DMA: ");
>          goto out;
>      }
>  
> @@ -1032,7 +1031,7 @@ static coroutine_fn int nvme_cmd_map_qiov(BlockDriverState *bs, NvmeCmd *cmd,
>  try_map:
>          r = qemu_vfio_dma_map(s->vfio,
>                                qiov->iov[i].iov_base,
> -                              len, true, &iova);
> +                              len, true, &iova, NULL);
>          if (r == -ENOSPC) {
>              /*
>               * In addition to the -ENOMEM error, the VFIO_IOMMU_MAP_DMA
> @@ -1524,14 +1523,15 @@ static void nvme_aio_unplug(BlockDriverState *bs)
>  static void nvme_register_buf(BlockDriverState *bs, void *host, size_t size)
>  {
>      int ret;
> +    Error *local_err = NULL;
>      BDRVNVMeState *s = bs->opaque;
>  
> -    ret = qemu_vfio_dma_map(s->vfio, host, size, false, NULL);
> +    ret = qemu_vfio_dma_map(s->vfio, host, size, false, NULL, &local_err);
>      if (ret) {
>          /* FIXME: we may run out of IOVA addresses after repeated
>           * bdrv_register_buf/bdrv_unregister_buf, because nvme_vfio_dma_unmap
>           * doesn't reclaim addresses for fixed mappings. */
> -        error_report("nvme_register_buf failed: %s", strerror(-ret));
> +        error_reportf_err(local_err, "nvme_register_buf failed: ");
>      }
>  }
>  
> diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> index e7909222cfd..77cdec845d9 100644
> --- a/util/vfio-helpers.c
> +++ b/util/vfio-helpers.c
> @@ -463,13 +463,15 @@ static void qemu_vfio_ram_block_added(RAMBlockNotifier *n, void *host,
>                                        size_t size, size_t max_size)
>  {
>      QEMUVFIOState *s = container_of(n, QEMUVFIOState, ram_notifier);
> +    Error *local_err = NULL;
>      int ret;
>  
>      trace_qemu_vfio_ram_block_added(s, host, max_size);
> -    ret = qemu_vfio_dma_map(s, host, max_size, false, NULL);
> +    ret = qemu_vfio_dma_map(s, host, max_size, false, NULL, &local_err);
>      if (ret) {
> -        error_report("qemu_vfio_dma_map(%p, %zu) failed: %s", host, max_size,
> -                     strerror(-ret));
> +        error_reportf_err(local_err,
> +                          "qemu_vfio_dma_map(%p, %zu) failed: ",
> +                          host, max_size);
>      }
>  }
>  
> @@ -725,7 +727,7 @@ qemu_vfio_find_temp_iova(QEMUVFIOState *s, size_t size, uint64_t *iova)
>   * mapping status within this area is not allowed).
>   */
>  int qemu_vfio_dma_map(QEMUVFIOState *s, void *host, size_t size,
> -                      bool temporary, uint64_t *iova)
> +                      bool temporary, uint64_t *iova, Error **errp)

Won't this break at this point? You add an Error** to qemu_vfio_dma_map,
but it is never used (so it probably stays NULL). So, above, if
qemu_vfio_dma_map() returns something not zero, you use error_prepend(),
which I think expects errp to be non-NULL?

I realize that later patches fixes this, but this sticks out when
reviewing this on its own.

>  {
>      int ret = 0;
>      int index;
> -- 
> 2.31.1
> 
> 


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