Re: [Qemu-devel] [PATCH v2 01/12] vfio/pci: Use local error object in vfio_initfn

[Markus Armbruster <armbru@redhat.com>]

Eric Auger <eric.auger@redhat.com> writes:

> To prepare for migration to realize, let's use a local error
> object in vfio_initfn. Also let's use the same error prefix for all
> error messages.
>
> On top of the 1-1 conversion, we start using a common error prefix for
> all error messages. We also introduce a similar warning prefix which will
> be used later on.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>
> v2: creation
> ---
>  hw/vfio/pci.c                 | 73 +++++++++++++++++++++++++------------------
>  include/hw/vfio/vfio-common.h |  3 ++
>  2 files changed, 46 insertions(+), 30 deletions(-)
>
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index a5a620a..ca0293d 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2493,6 +2493,7 @@ static int vfio_initfn(PCIDevice *pdev)
>      VFIODevice *vbasedev_iter;
>      VFIOGroup *group;
>      char *tmp, group_path[PATH_MAX], *group_name;
> +    Error *err = NULL;
>      ssize_t len;
>      struct stat st;
>      int groupid;
> @@ -2506,9 +2507,9 @@ static int vfio_initfn(PCIDevice *pdev)
>      }
>  
>      if (stat(vdev->vbasedev.sysfsdev, &st) < 0) {
> -        error_report("vfio: error: no such host device: %s",
> -                     vdev->vbasedev.sysfsdev);
> -        return -errno;
> +        error_setg(&err, "no such host device");

Any particular reason you don't use error_setg_errno() here?

> +        ret = -errno;
> +        goto error;
>      }
>  
>      vdev->vbasedev.name = g_strdup(basename(vdev->vbasedev.sysfsdev));
> @@ -2520,40 +2521,44 @@ static int vfio_initfn(PCIDevice *pdev)
>      g_free(tmp);
>  
>      if (len <= 0 || len >= sizeof(group_path)) {
> -        error_report("vfio: error no iommu_group for device");
> -        return len < 0 ? -errno : -ENAMETOOLONG;
> +        error_setg_errno(&err, len < 0 ? errno : ENAMETOOLONG,
> +                         "no iommu_group found");
> +        ret = len < 0 ? -errno : -ENAMETOOLONG;

Suggest

           ret = len < 0 ? -errno : -ENAMETOOLONG;
           error_setg_errno(&err, -ret, "no iommu_group found");

> +        goto error;
>      }
>  
>      group_path[len] = 0;
>  
>      group_name = basename(group_path);
>      if (sscanf(group_name, "%d", &groupid) != 1) {
> -        error_report("vfio: error reading %s: %m", group_path);
> -        return -errno;
> +        error_setg_errno(&err, errno, "failed to read %s", group_path);
> +        ret = -errno;
> +        goto error;
>      }
>  
>      trace_vfio_initfn(vdev->vbasedev.name, groupid);
>  
>      group = vfio_get_group(groupid, pci_device_iommu_address_space(pdev));
>      if (!group) {
> -        error_report("vfio: failed to get group %d", groupid);
> -        return -ENOENT;
> +        error_setg(&err, "failed to get group %d", groupid);
> +        ret = -ENOENT;
> +        goto error;
>      }
>  
>      QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
>          if (strcmp(vbasedev_iter->name, vdev->vbasedev.name) == 0) {
> -            error_report("vfio: error: device %s is already attached",
> -                         vdev->vbasedev.name);
> +            error_setg(&err, "device is already attached");
>              vfio_put_group(group);
> -            return -EBUSY;
> +            ret = -EBUSY;
> +            goto error;
>          }
>      }
>  
>      ret = vfio_get_device(group, vdev->vbasedev.name, &vdev->vbasedev);
>      if (ret) {
> -        error_report("vfio: failed to get device %s", vdev->vbasedev.name);
> +        error_setg_errno(&err, -ret, "failed to get device");
>          vfio_put_group(group);
> -        return ret;
> +        goto error;
>      }
>  
>      ret = vfio_populate_device(vdev);
> @@ -2567,8 +2572,8 @@ static int vfio_initfn(PCIDevice *pdev)
>                  vdev->config_offset);
>      if (ret < (int)MIN(pci_config_size(&vdev->pdev), vdev->config_size)) {
>          ret = ret < 0 ? -errno : -EFAULT;
> -        error_report("vfio: Failed to read device config space");
> -        return ret;
> +        error_setg_errno(&err, -ret, "failed to read device config space");
> +        goto error;
>      }
>  
>      /* vfio emulates a lot for us, but some bits need extra love */
> @@ -2584,8 +2589,9 @@ static int vfio_initfn(PCIDevice *pdev)
>       */
>      if (vdev->vendor_id != PCI_ANY_ID) {
>          if (vdev->vendor_id >= 0xffff) {
> -            error_report("vfio: Invalid PCI vendor ID provided");
> -            return -EINVAL;
> +            error_setg(&err, "invalid PCI vendor ID provided");
> +            ret = -EINVAL;
> +            goto error;
>          }
>          vfio_add_emulated_word(vdev, PCI_VENDOR_ID, vdev->vendor_id, ~0);
>          trace_vfio_pci_emulated_vendor_id(vdev->vbasedev.name, vdev->vendor_id);
> @@ -2595,8 +2601,9 @@ static int vfio_initfn(PCIDevice *pdev)
>  
>      if (vdev->device_id != PCI_ANY_ID) {
>          if (vdev->device_id > 0xffff) {
> -            error_report("vfio: Invalid PCI device ID provided");
> -            return -EINVAL;
> +            error_setg(&err, "invalid PCI device ID provided");
> +            ret = -EINVAL;
> +            goto error;
>          }
>          vfio_add_emulated_word(vdev, PCI_DEVICE_ID, vdev->device_id, ~0);
>          trace_vfio_pci_emulated_device_id(vdev->vbasedev.name, vdev->device_id);
> @@ -2606,8 +2613,9 @@ static int vfio_initfn(PCIDevice *pdev)
>  
>      if (vdev->sub_vendor_id != PCI_ANY_ID) {
>          if (vdev->sub_vendor_id > 0xffff) {
> -            error_report("vfio: Invalid PCI subsystem vendor ID provided");
> -            return -EINVAL;
> +            error_setg(&err, "invalid PCI subsystem vendor ID provided");
> +            ret = -EINVAL;
> +            goto error;
>          }
>          vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_VENDOR_ID,
>                                 vdev->sub_vendor_id, ~0);
> @@ -2617,8 +2625,9 @@ static int vfio_initfn(PCIDevice *pdev)
>  
>      if (vdev->sub_device_id != PCI_ANY_ID) {
>          if (vdev->sub_device_id > 0xffff) {
> -            error_report("vfio: Invalid PCI subsystem device ID provided");
> -            return -EINVAL;
> +            error_setg(&err, "invalid PCI subsystem device ID provided");
> +            ret = -EINVAL;
> +            goto error;
>          }
>          vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_ID, vdev->sub_device_id, ~0);
>          trace_vfio_pci_emulated_sub_device_id(vdev->vbasedev.name,
> @@ -2671,8 +2680,9 @@ static int vfio_initfn(PCIDevice *pdev)
>          struct vfio_region_info *opregion;
>  
>          if (vdev->pdev.qdev.hotplugged) {
> -            error_report("Cannot support IGD OpRegion feature on hotplugged "
> -                         "device %s", vdev->vbasedev.name);
> +            error_setg(&err,
> +                       "cannot support IGD OpRegion feature on hotplugged "
> +                       "device");
>              ret = -EINVAL;
>              goto out_teardown;
>          }
> @@ -2681,16 +2691,15 @@ static int vfio_initfn(PCIDevice *pdev)
>                          VFIO_REGION_TYPE_PCI_VENDOR_TYPE | PCI_VENDOR_ID_INTEL,
>                          VFIO_REGION_SUBTYPE_INTEL_IGD_OPREGION, &opregion);
>          if (ret) {
> -            error_report("Device %s does not support requested IGD OpRegion "
> -                         "feature", vdev->vbasedev.name);
> +            error_setg_errno(&err, -ret,
> +                             "does not support requested IGD OpRegion feature");
>              goto out_teardown;
>          }
>  
>          ret = vfio_pci_igd_opregion_init(vdev, opregion);
>          g_free(opregion);
>          if (ret) {
> -            error_report("Device %s IGD OpRegion initialization failed",
> -                         vdev->vbasedev.name);
> +            error_setg_errno(&err, -ret, "IGD OpRegion initialization failed");
>              goto out_teardown;
>          }
>      }
> @@ -2726,6 +2735,10 @@ out_teardown:
>      pci_device_set_intx_routing_notifier(&vdev->pdev, NULL);
>      vfio_teardown_msi(vdev);
>      vfio_bars_exit(vdev);
> +error:
> +    if (err) {
> +        error_reportf_err(err, ERR_PREFIX, vdev->vbasedev.name);
> +    }
>      return ret;
>  }

The value assigned to ret doesn't matter as long as it's negative, which
makes me wonder why we bother with different values here.  Peeking
ahead, I see you simplify this already as part of your conversion to
realize().  Okay, that works for me.

>  
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 94dfae3..fd19880 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -30,6 +30,9 @@
>  #include <linux/vfio.h>
>  #endif
>  
> +#define ERR_PREFIX "vfio error: %s: "
> +#define WARN_PREFIX "vfio warning: %s: "
> +
>  /*#define DEBUG_VFIO*/
>  #ifdef DEBUG_VFIO
>  #define DPRINTF(fmt, ...) \

We already discussed error message prefixes and errno strings.  I got my
taste, you got yours.  Since this is your code, yours wins :)