Re: [Qemu-devel] [PATCH v2 09/12] vfio/pci: Conversion to realize

[Auger Eric <eric.auger@redhat.com>]

Hi,

On 22/09/2016 19:24, Markus Armbruster wrote:
> Eric Auger <eric.auger@redhat.com> writes:
> 
>> This patch converts VFIO PCI to realize function.
>>
>> Also original initfn errors now are propagated using QEMU
>> error objects. All errors are formatted with the same pattern:
>> "vfio: %s: the error description"
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>
>> ---
>>
>> v1 -> v2:
>> - correct error_setg_errno with positive error values
>> ---
>>  hw/vfio/pci.c        | 52 ++++++++++++++++++++++------------------------------
>>  hw/vfio/trace-events |  2 +-
>>  2 files changed, 23 insertions(+), 31 deletions(-)
>>
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index 3d43718..857d89f 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -2511,7 +2511,7 @@ static void vfio_unregister_req_notifier(VFIOPCIDevice *vdev)
>>      vdev->req_enabled = false;
>>  }
>>  
>> -static int vfio_initfn(PCIDevice *pdev)
>> +static void vfio_realize(PCIDevice *pdev, Error **errp)
>>  {
>>      VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
>>      VFIODevice *vbasedev_iter;
>> @@ -2531,9 +2531,9 @@ static int vfio_initfn(PCIDevice *pdev)
>>      }
>>  
>>      if (stat(vdev->vbasedev.sysfsdev, &st) < 0) {
>> -        error_setg(&err, "no such host device");
>> -        ret = -errno;
>> -        goto error;
>> +        error_setg(errp, "no such host device");
>> +        error_prepend(errp, ERR_PREFIX, vdev->vbasedev.sysfsdev);
>> +        return;
> 
> Could do
> 
>            error_setg(errp, "no such host device");
>            goto error;
> 
> Your choice.
At that stage the vdev->vbasedev.name is not populated yet.
> 
>>      }
>>  
>>      vdev->vbasedev.name = g_strdup(basename(vdev->vbasedev.sysfsdev));
>> @@ -2545,9 +2545,8 @@ static int vfio_initfn(PCIDevice *pdev)
>>      g_free(tmp);
>>  
>>      if (len <= 0 || len >= sizeof(group_path)) {
>> -        error_setg_errno(&err, len < 0 ? errno : ENAMETOOLONG,
>> +        error_setg_errno(errp, len < 0 ? errno : ENAMETOOLONG,
>>                           "no iommu_group found");
>> -        ret = len < 0 ? -errno : -ENAMETOOLONG;
>>          goto error;
>>      }
>>  
> 
> Due to this change and others below, ret is no longer valid at the error
> label (fine, it's not used), and the error is set either via err or via
> errp.  Works, because error_propagate(errp, err) does the right thing
> then: nothing when err is null.  However, changing the goto to jump
> behind the error_propagate when using errp rather than err might be
> clearer.
Let's use a local error when I can't do otherwise then.
> 
> Continuing to set the error via err also works.  Less churn.
> 
> Your choice.
> 
>> @@ -2555,24 +2554,21 @@ static int vfio_initfn(PCIDevice *pdev)
>>  
>>      group_name = basename(group_path);
>>      if (sscanf(group_name, "%d", &groupid) != 1) {
>> -        error_setg_errno(&err, errno, "failed to read %s", group_path);
>> -        ret = -errno;
>> +        error_setg_errno(errp, errno, "failed to read %s", group_path);
>>          goto error;
>>      }
>>  
>> -    trace_vfio_initfn(vdev->vbasedev.name, groupid);
>> +    trace_vfio_realize(vdev->vbasedev.name, groupid);
>>  
>>      group = vfio_get_group(groupid, pci_device_iommu_address_space(pdev), &err);
>>      if (!group) {
>> -        ret = -ENOENT;
>>          goto error;
>>      }
> 
> Since you don't examine the error, you could use errp rather than &err.
> Perhaps not worth the churn unless you can get rid of err entirely.
Not possible to completely get rid of local err due to
vfio_pci_igd_opregion_init - since can't dereference errp  -but I can do
a local error_propagate.
> 
>>  
>>      QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
>>          if (strcmp(vbasedev_iter->name, vdev->vbasedev.name) == 0) {
>> -            error_setg(&err, "device is already attached");
>> +            error_setg(errp, "device is already attached");
>>              vfio_put_group(group);
>> -            ret = -EBUSY;
>>              goto error;
>>          }
>>      }
>> @@ -2594,7 +2590,7 @@ 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_setg_errno(&err, -ret, "failed to read device config space");
>> +        error_setg_errno(errp, -ret, "failed to read device config space");
>>          goto error;
>>      }
>>  
>> @@ -2611,8 +2607,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>       */
>>      if (vdev->vendor_id != PCI_ANY_ID) {
>>          if (vdev->vendor_id >= 0xffff) {
>> -            error_setg(&err, "invalid PCI vendor ID provided");
>> -            ret = -EINVAL;
>> +            error_setg(errp, "invalid PCI vendor ID provided");
>>              goto error;
>>          }
>>          vfio_add_emulated_word(vdev, PCI_VENDOR_ID, vdev->vendor_id, ~0);
>> @@ -2623,8 +2618,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>  
>>      if (vdev->device_id != PCI_ANY_ID) {
>>          if (vdev->device_id > 0xffff) {
>> -            error_setg(&err, "invalid PCI device ID provided");
>> -            ret = -EINVAL;
>> +            error_setg(errp, "invalid PCI device ID provided");
>>              goto error;
>>          }
>>          vfio_add_emulated_word(vdev, PCI_DEVICE_ID, vdev->device_id, ~0);
>> @@ -2635,8 +2629,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>  
>>      if (vdev->sub_vendor_id != PCI_ANY_ID) {
>>          if (vdev->sub_vendor_id > 0xffff) {
>> -            error_setg(&err, "invalid PCI subsystem vendor ID provided");
>> -            ret = -EINVAL;
>> +            error_setg(errp, "invalid PCI subsystem vendor ID provided");
>>              goto error;
>>          }
>>          vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_VENDOR_ID,
>> @@ -2647,8 +2640,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>  
>>      if (vdev->sub_device_id != PCI_ANY_ID) {
>>          if (vdev->sub_device_id > 0xffff) {
>> -            error_setg(&err, "invalid PCI subsystem device ID provided");
>> -            ret = -EINVAL;
>> +            error_setg(errp, "invalid PCI subsystem device ID provided");
>>              goto error;
>>          }
>>          vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_ID, vdev->sub_device_id, ~0);
>> @@ -2702,10 +2694,9 @@ static int vfio_initfn(PCIDevice *pdev)
>>          struct vfio_region_info *opregion;
>>  
>>          if (vdev->pdev.qdev.hotplugged) {
>> -            error_setg(&err,
>> +            error_setg(errp,
>>                         "cannot support IGD OpRegion feature on hotplugged "
>>                         "device");
>> -            ret = -EINVAL;
>>              goto out_teardown;
>>          }
>>  
>> @@ -2713,7 +2704,7 @@ 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_setg_errno(&err, -ret,
>> +            error_setg_errno(errp, -ret,
>>                               "does not support requested IGD OpRegion feature");
>>              goto out_teardown;
>>          }
>> @@ -2721,7 +2712,6 @@ static int vfio_initfn(PCIDevice *pdev)
>>          vfio_pci_igd_opregion_init(vdev, opregion, &err);
>>          g_free(opregion);
>>          if (err) {
>> -            ret = -EINVAL;
>>              goto out_teardown;
>>          }
>>      }
>> @@ -2743,6 +2733,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>          pci_device_set_intx_routing_notifier(&vdev->pdev, vfio_intx_update);
>>          ret = vfio_intx_enable(vdev, &err);
>>          if (ret) {
>> +            error_setg_errno(errp, -ret, "failed to enable intx");
> 
> If vfio_intx_enable() sets an error on any failure (as it should), then
> the later error_propagate(errp, err) will simply free err.  Adding the
> error_setg_errno() here overrides the specific error set by
> vfio_intx_enable() with a generic one.  Looks wrong to me.
Yes this is definitively wrong!
> 
> If it doesn't, then the error_propagate() will work around that
> misbehavior.  You should fix vfio_intx_enable() then.
> 
>>              goto out_teardown;
>>          }
>>      }
>> @@ -2751,17 +2742,18 @@ static int vfio_initfn(PCIDevice *pdev)
>>      vfio_register_req_notifier(vdev);
>>      vfio_setup_resetfn_quirk(vdev);
>>  
>> -    return 0;
>> +    return;
>>  
>>  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);
>> +    error_propagate(errp, err);
>> +
>> +    if (*errp) {
>> +        error_prepend(errp, ERR_PREFIX, vdev->vbasedev.name);
>>      }
> 
> Dereferencing errp is unclean, because callers may pass null to ignore
> errors.  The qdev core doesn't.  However, error_prepend() does the right
> thing when passed null, namely nothing.  Simply call it unconditionally.
understood.

Thank you for your time!

Best Regards

Eric
> 
>> -    return ret;
>>  }
>>  
>>  static void vfio_instance_finalize(Object *obj)
>> @@ -2890,7 +2882,7 @@ static void vfio_pci_dev_class_init(ObjectClass *klass, void *data)
>>      dc->vmsd = &vfio_pci_vmstate;
>>      dc->desc = "VFIO-based PCI device assignment";
>>      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
>> -    pdc->init = vfio_initfn;
>> +    pdc->realize = vfio_realize;
>>      pdc->exit = vfio_exitfn;
>>      pdc->config_read = vfio_pci_read_config;
>>      pdc->config_write = vfio_pci_write_config;
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index da13322..ef81609 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -36,7 +36,7 @@ vfio_pci_hot_reset_dep_devices(int domain, int bus, int slot, int function, int
>>  vfio_pci_hot_reset_result(const char *name, const char *result) "%s hot reset: %s"
>>  vfio_populate_device_config(const char *name, unsigned long size, unsigned long offset, unsigned long flags) "Device %s config:\n  size: 0x%lx, offset: 0x%lx, flags: 0x%lx"
>>  vfio_populate_device_get_irq_info_failure(void) "VFIO_DEVICE_GET_IRQ_INFO failure: %m"
>> -vfio_initfn(const char *name, int group_id) " (%s) group %d"
>> +vfio_realize(const char *name, int group_id) " (%s) group %d"
>>  vfio_add_ext_cap_dropped(const char *name, uint16_t cap, uint16_t offset) "%s %x@%x"
>>  vfio_pci_reset(const char *name) " (%s)"
>>  vfio_pci_reset_flr(const char *name) "%s FLR/VFIO_DEVICE_RESET"
>