Re: [PATCH v2 11/19] util/vfio-helpers: Let qemu_vfio_dma_map() propagate Error

[Auger Eric]

Hi Philippe,

On 10/26/20 11:54 AM, 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* argument so it can
Error** or simply error handle
> 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                | 14 +++++++-------
>  util/vfio-helpers.c         | 12 +++++++-----
>  3 files changed, 15 insertions(+), 13 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 3b6d3972ec2..6f1ebdf031f 100644
> --- a/block/nvme.c
> +++ b/block/nvme.c
> @@ -167,9 +167,9 @@ static void nvme_init_queue(BDRVNVMeState *s, NVMeQueue 
> *q,
>          return;
>      }
>      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");
> +        error_prepend(errp, "Cannot map queue: ");
>      }
>  }
>  
> @@ -223,7 +223,7 @@ static NVMeQueuePair 
> *nvme_create_queue_pair(BDRVNVMeState *s,
>      q->completion_bh = aio_bh_new(aio_context, nvme_process_completion_bh, 
> q);
>      r = qemu_vfio_dma_map(s->vfio, q->prp_list_pages,
>                            s->page_size * NVME_NUM_REQS,
> -                          false, &prp_list_iova);
> +                          false, &prp_list_iova, errp);
>      if (r) {
you may add an associated error_prepend(errp, "") here too to be consistent.
>          goto fail;
>      }
> @@ -514,9 +514,9 @@ static void 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, sizeof(*id), true, &iova);
> +    r = qemu_vfio_dma_map(s->vfio, id, sizeof(*id), true, &iova, errp);
>      if (r) {
> -        error_setg(errp, "Cannot map buffer for DMA");
> +        error_prepend(errp, "Cannot map buffer for DMA: ");
>          goto out;
>      }
>  
> @@ -1003,7 +1003,7 @@ try_map:
>          r = qemu_vfio_dma_map(s->vfio,
>                                qiov->iov[i].iov_base,
>                                qiov->iov[i].iov_len,
> -                              true, &iova);
> +                              true, &iova, NULL);
>          if (r == -ENOMEM && retry) {
>              retry = false;
>              trace_nvme_dma_flush_queue_wait(s);
> @@ -1450,7 +1450,7 @@ static void nvme_register_buf(BlockDriverState *bs, 
> void *host, size_t size)
>      int ret;
>      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, NULL);
>      if (ret) {
>          /* FIXME: we may run out of IOVA addresses after repeated
>           * bdrv_register_buf/bdrv_unregister_buf, because nvme_vfio_dma_unmap
> diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
> index 73f7bfa7540..c03fe0b7156 100644
> --- a/util/vfio-helpers.c
> +++ b/util/vfio-helpers.c
> @@ -462,7 +462,7 @@ static void qemu_vfio_ram_block_added(RAMBlockNotifier *n,
>  {
>      QEMUVFIOState *s = container_of(n, QEMUVFIOState, ram_notifier);
>      trace_qemu_vfio_ram_block_added(s, host, size);
> -    qemu_vfio_dma_map(s, host, size, false, NULL);
> +    qemu_vfio_dma_map(s, host, size, false, NULL, NULL);
>  }
>  
>  static void qemu_vfio_ram_block_removed(RAMBlockNotifier *n,
> @@ -477,6 +477,7 @@ static void qemu_vfio_ram_block_removed(RAMBlockNotifier 
> *n,
>  
>  static int qemu_vfio_init_ramblock(RAMBlock *rb, void *opaque)
>  {
> +    Error *local_err = NULL;
>      void *host_addr = qemu_ram_get_host_addr(rb);
>      ram_addr_t length = qemu_ram_get_used_length(rb);
>      int ret;
> @@ -485,10 +486,11 @@ static int qemu_vfio_init_ramblock(RAMBlock *rb, void 
> *opaque)
>      if (!host_addr) {
>          return 0;
>      }
> -    ret = qemu_vfio_dma_map(s, host_addr, length, false, NULL);
> +    ret = qemu_vfio_dma_map(s, host_addr, length, false, NULL, &local_err);
>      if (ret) {
> -        fprintf(stderr, "qemu_vfio_init_ramblock: failed %p %" PRId64 "\n",
> -                host_addr, (uint64_t)length);
> +        error_reportf_err(local_err,
> +                          "qemu_vfio_init_ramblock: failed %p %" PRId64 ":",
> +                          host_addr, (uint64_t)length);
>      }
>      return 0;
>  }
> @@ -724,7 +726,7 @@ 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)
>  {
where do you set errp. You just add prepend messages above. If I am not
wrong errp must be non NULL to call error_prepend()

Thanks

Eric
>      int ret = 0;
>      int index;
>