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

[Klaus Jensen]

On Aug 27 08:24, Philippe Mathieu-Daudé wrote:
> +Markus
> 
> On 8/27/21 7:48 AM, Klaus Jensen wrote:
> > 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 can't find such restriction documented in "qapi/error.h".
> 
> In error.c:
> 
> void error_prepend(Error *const *errp, const char *fmt, ...)
> {
>     va_list ap;
> 
>     va_start(ap, fmt);
>     error_vprepend(errp, fmt, ap);
>     ...
> 
> void error_vprepend(Error *const *errp, const char *fmt, va_list ap)
> {
>     GString *newmsg;
> 
>     if (!errp) {
>         return;
>     }
>     ...
> 

Sorry, my bad - I should have checked myself. In that case,

Reviewed-by: Klaus Jensen <k.jensen@samsung.com>

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