Re: [Qemu-devel] [PATCH v2 05/12] vfio/pci: Pass an error object to vfio_add_capabilities

[Markus Armbruster <armbru@redhat.com>]

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

> Pass an error object to prepare for migration to VFIO-PCI realize.
> The error is cascaded downto vfio_add_std_cap and then vfio_msi(x)_setup,
> vfio_setup_pcie_cap.
>
> vfio_add_ext_cap does not return anything else than 0 so let's transform
> it into a void function.
>
> Also use pci_add_capability2 which takes an error object.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/vfio/pci.c | 66 ++++++++++++++++++++++++++++++++---------------------------
>  1 file changed, 36 insertions(+), 30 deletions(-)
>
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index f67eec4..07a44f5 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -1178,7 +1178,7 @@ static void vfio_disable_interrupts(VFIOPCIDevice *vdev)
>      }
>  }
>  
> -static int vfio_msi_setup(VFIOPCIDevice *vdev, int pos)
> +static int vfio_msi_setup(VFIOPCIDevice *vdev, int pos, Error **errp)
>  {
>      uint16_t ctrl;
>      bool msi_64bit, msi_maskbit;
       int ret, entries;
       Error *err = NULL;

       if (pread(vdev->vbasedev.fd, &ctrl, sizeof(ctrl),
                 vdev->config_offset + pos + PCI_CAP_FLAGS) != sizeof(ctrl)) {
           return -errno;
       }

Fails without setting error here.

> @@ -1202,8 +1202,7 @@ static int vfio_msi_setup(VFIOPCIDevice *vdev, int pos)
>          if (ret == -ENOTSUP) {
>              return 0;
>          }
> -        error_prepend(&err, "vfio: msi_init failed: ");
> -        error_report_err(err);
> +        error_propagate(errp, err);
>          return ret;
>      }
>      vdev->msi_cap_size = 0xa + (msi_maskbit ? 0xa : 0) + (msi_64bit ? 0x4 : 0);
> @@ -1361,7 +1360,7 @@ static int vfio_msix_early_setup(VFIOPCIDevice *vdev, Error **errp)
>      return 0;
>  }
>  
> -static int vfio_msix_setup(VFIOPCIDevice *vdev, int pos)
> +static int vfio_msix_setup(VFIOPCIDevice *vdev, int pos, Error **errp)
>  {
>      int ret;
>  
> @@ -1376,7 +1375,7 @@ static int vfio_msix_setup(VFIOPCIDevice *vdev, int pos)
>          if (ret == -ENOTSUP) {
>              return 0;
>          }
> -        error_report("vfio: msix_init failed");
> +        error_setg(errp, "msix_init failed");
>          return ret;
>      }
>  
> @@ -1561,7 +1560,8 @@ static void vfio_add_emulated_long(VFIOPCIDevice *vdev, int pos,
>      vfio_set_long_bits(vdev->emulated_config_bits + pos, mask, mask);
>  }
>  
> -static int vfio_setup_pcie_cap(VFIOPCIDevice *vdev, int pos, uint8_t size)
> +static int vfio_setup_pcie_cap(VFIOPCIDevice *vdev, int pos, uint8_t size,
> +                               Error **errp)
>  {
>      uint16_t flags;
>      uint8_t type;
> @@ -1573,8 +1573,8 @@ static int vfio_setup_pcie_cap(VFIOPCIDevice *vdev, int pos, uint8_t size)
>          type != PCI_EXP_TYPE_LEG_END &&
>          type != PCI_EXP_TYPE_RC_END) {
>  
> -        error_report("vfio: Assignment of PCIe type 0x%x "
> -                     "devices is not currently supported", type);
> +        error_setg(errp, "assignment of PCIe type 0x%x "
> +                   "devices is not currently supported", type);
>          return -EINVAL;
>      }
>  
> @@ -1708,10 +1708,11 @@ static void vfio_check_af_flr(VFIOPCIDevice *vdev, uint8_t pos)
>      }
>  }
>  
> -static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos)
> +static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos, Error **errp)
>  {
>      PCIDevice *pdev = &vdev->pdev;
>      uint8_t cap_id, next, size;
> +    Error *err = NULL;
>      int ret;
>  
>      cap_id = pdev->config[pos];
> @@ -1733,9 +1734,9 @@ static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos)
>       * will be changed as we unwind the stack.
>       */
>      if (next) {
> -        ret = vfio_add_std_cap(vdev, next);
> +        ret = vfio_add_std_cap(vdev, next, &err);
>          if (ret) {
> -            return ret;
> +            goto out;
>          }
>      } else {
>          /* Begin the rebuild, use QEMU emulated list bits */
> @@ -1749,40 +1750,42 @@ static int vfio_add_std_cap(VFIOPCIDevice *vdev, uint8_t pos)
>  
>      switch (cap_id) {
>      case PCI_CAP_ID_MSI:
> -        ret = vfio_msi_setup(vdev, pos);
> +        ret = vfio_msi_setup(vdev, pos, &err);
>          break;
>      case PCI_CAP_ID_EXP:
>          vfio_check_pcie_flr(vdev, pos);
> -        ret = vfio_setup_pcie_cap(vdev, pos, size);
> +        ret = vfio_setup_pcie_cap(vdev, pos, size, &err);
>          break;
>      case PCI_CAP_ID_MSIX:
> -        ret = vfio_msix_setup(vdev, pos);
> +        ret = vfio_msix_setup(vdev, pos, &err);
>          break;
>      case PCI_CAP_ID_PM:
>          vfio_check_pm_reset(vdev, pos);
>          vdev->pm_cap = pos;
> -        ret = pci_add_capability(pdev, cap_id, pos, size);
> +        ret = pci_add_capability2(pdev, cap_id, pos, size, &err);
>          break;
>      case PCI_CAP_ID_AF:
>          vfio_check_af_flr(vdev, pos);
> -        ret = pci_add_capability(pdev, cap_id, pos, size);
> +        ret = pci_add_capability2(pdev, cap_id, pos, size, &err);
>          break;
>      default:
> -        ret = pci_add_capability(pdev, cap_id, pos, size);
> +        ret = pci_add_capability2(pdev, cap_id, pos, size, &err);
>          break;
>      }
>  
> -    if (ret < 0) {
> -        error_report("vfio: %s Error adding PCI capability "
> -                     "0x%x[0x%x]@0x%x: %d", vdev->vbasedev.name,
> -                     cap_id, size, pos, ret);
> -        return ret;
> +out:
> +    error_propagate(errp, err);
> +    if (*errp) {
> +        error_prepend(errp,
> +                      "failed to add PCI capability 0x%x[0x%x]@0x%x: ",
> +                      cap_id, size, pos);
>      }

Less verbose, and therefore recommended by the big comment in error.h is
using errp instead of &err, then

   out:
       if (ret < 0) {
           error_prepend(errp,
                         "failed to add PCI capability 0x%x[0x%x]@0x%x: ",
                         cap_id, size, pos);
       }

Adding the error_propagate() now anyway can make sense when you get rid
of ret later in the series.

>  
> -    return 0;
> +    return ret < 0 ? ret : 0;
> +

Spurious blank line.

>  }
>  
> -static int vfio_add_ext_cap(VFIOPCIDevice *vdev)
> +static void vfio_add_ext_cap(VFIOPCIDevice *vdev)
>  {
>      PCIDevice *pdev = &vdev->pdev;
>      uint32_t header;
> @@ -1793,7 +1796,7 @@ static int vfio_add_ext_cap(VFIOPCIDevice *vdev)
>      /* Only add extended caps if we have them and the guest can see them */
>      if (!pci_is_express(pdev) || !pci_bus_is_express(pdev->bus) ||
>          !pci_get_long(pdev->config + PCI_CONFIG_SPACE_SIZE)) {
> -        return 0;
> +        return;
>      }
>  
>      /*
> @@ -1858,12 +1861,13 @@ static int vfio_add_ext_cap(VFIOPCIDevice *vdev)
>      }
>  
>      g_free(config);
> -    return 0;
> +    return;
>  }
>  
> -static int vfio_add_capabilities(VFIOPCIDevice *vdev)
> +static int vfio_add_capabilities(VFIOPCIDevice *vdev, Error **errp)
>  {
>      PCIDevice *pdev = &vdev->pdev;
> +    Error *err = NULL;
>      int ret;
>  
>      if (!(pdev->config[PCI_STATUS] & PCI_STATUS_CAP_LIST) ||
> @@ -1871,12 +1875,14 @@ static int vfio_add_capabilities(VFIOPCIDevice *vdev)
>          return 0; /* Nothing to add */
>      }
>  
> -    ret = vfio_add_std_cap(vdev, pdev->config[PCI_CAPABILITY_LIST]);
> +    ret = vfio_add_std_cap(vdev, pdev->config[PCI_CAPABILITY_LIST], &err);
>      if (ret) {
> +        error_propagate(errp, err);
>          return ret;
>      }

Likewise, as long as you have (and intend to keep) ret, do

       ret = vfio_add_std_cap(vdev, pdev->config[PCI_CAPABILITY_LIST], errp);
       if (ret) {
           return ret;
       }

>  
> -    return vfio_add_ext_cap(vdev);
> +    vfio_add_ext_cap(vdev);
> +    return 0;
>  }
>  
>  static void vfio_pci_pre_reset(VFIOPCIDevice *vdev)
> @@ -2680,7 +2686,7 @@ static int vfio_initfn(PCIDevice *pdev)
>  
>      vfio_bars_setup(vdev);
>  
> -    ret = vfio_add_capabilities(vdev);
> +    ret = vfio_add_capabilities(vdev, &err);
>      if (ret) {
>          goto out_teardown;
>      }