Re: [Qemu-devel] [PATCH 1/3] vfio/pci: conversion to realize

[Auger Eric]

Hi Markus,

On 12/09/2016 14:45, Markus Armbruster wrote:
> Eric Auger <address@hidden> 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"
> 
> Example:
> 
> $ upstream-qemu -device vfio-pci
> upstream-qemu: -device vfio-pci: vfio: 0000:00:00.0: no iommu_group found: 
> Unknown error -2
> 
> Two remarks:
> 
> * "Unknown error -2" should be "No such file or directory".  See below.
Hum. I noticed that but I didn't have the presence of mind to get it was
due to -errno!
> 
> * Five colons, not counting the ones in the PCI address.  Do we need the
>   "vfio: 0000:00:00.0:" part?  If yes, could we find a nicer way to
>   print it?  Up to you.
Well we have quite a lot of traces with such format, hence my choice.
Alex do you want to change this?
> 
> Always, always, always test your error messages :)
> 
>> Subsequent patches will pass the error objects to
>> - vfio_populate_device,
>> - vfio_msix_early_setup.
>>
>> At this point if those functions fail let's just report an error
>> at realize level.
>>
>> Signed-off-by: Eric Auger <address@hidden>
>> ---
>>  hw/vfio/pci.c        | 81 
>> ++++++++++++++++++++++++++++------------------------
>>  hw/vfio/trace-events |  2 +-
>>  2 files changed, 44 insertions(+), 39 deletions(-)
>>
>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>> index 7bfa17c..ae1967c 100644
>> --- a/hw/vfio/pci.c
>> +++ b/hw/vfio/pci.c
>> @@ -2485,7 +2485,7 @@ 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;
>> @@ -2504,9 +2504,9 @@ 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_errno(errp, -errno, "vfio: error: no such host device: 
>> %s",
> 
> error_setg_errno() takes a *positive* errno.  Same elsewhere.
OK thanks!
> 
>> +                         vdev->vbasedev.sysfsdev);
>> +        return;
>>      }
>>  
>>      vdev->vbasedev.name = g_strdup(basename(vdev->vbasedev.sysfsdev));
>> @@ -2518,45 +2518,46 @@ 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(errp, len < 0 ? -errno : -ENAMETOOLONG,
>> +                         "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(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));
>>      if (!group) {
>> -        error_report("vfio: failed to get group %d", groupid);
>> -        return -ENOENT;
>> +        error_setg_errno(errp, -ENOENT, "failed to get group %d", groupid);
>> +        goto error;
> 
> I understand this is a mechanical conversion, but are you sure the ": No
> such file or directory" suffix we get from passing ENOENT buys us
> anything?  More of the same below.
At that stage I prefered to stick to the original messages since Alex &
VFIO users may have their habits.
> 
>>      }
>>  
>>      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_errno(errp, -EBUSY, "device is already attached");
>>              vfio_put_group(group);
>> -            return -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(errp, ret, "failed to get the device");
>>          vfio_put_group(group);
>> -        return ret;
>> +        goto error;
>>      }
>>  
>>      ret = vfio_populate_device(vdev);
>>      if (ret) {
>> -        return ret;
>> +        error_setg_errno(errp, ret, "failed to populate the device");
>> +        goto error;
>>      }
> 
> vfio_populate_device() reports errors with error_report().  We get a
> specific error via error_report(), and a generic error here.  PATCH 2
> converts it to Error, getting rid of the generic error again.  Works for
> me, but I usually order conversion patches the other way: first convert
> vfio_populate_device(), and report its Error like this:
> 
>     ret = vfio_populate_device(vdev, &err);
>     if (err) {
>         error_report_err(err);
>         return ret;
>     }
> 
> PRO: no intermediate state with two errors.  CON: have to touch
> vfio_populate_device() again to drop the return value.  Matter of taste,
> thus your choice.
> 
> Same for vfio_msix_early_setup() below.

Yes it makes sense. I will respin adopting the above strategy.
> 
>>  
>>      /* Get a copy of config space */
>> @@ -2565,8 +2566,8 @@ 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(errp, ret, "failed to read device config space");
>> +        goto error;
>>      }
>>  
>>      /* vfio emulates a lot for us, but some bits need extra love */
>> @@ -2582,8 +2583,8 @@ 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_errno(errp, -EINVAL, "invalid PCI vendor ID 
>> provided");
>> +            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);
>> @@ -2593,8 +2594,8 @@ 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_errno(errp, -EINVAL, "invalid PCI device ID 
>> provided");
>> +            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);
>> @@ -2604,8 +2605,9 @@ 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_errno(errp, -EINVAL,
>> +                             "invalid PCI subsystem vendor ID provided");
>> +            goto error;
>>          }
>>          vfio_add_emulated_word(vdev, PCI_SUBSYSTEM_VENDOR_ID,
>>                                 vdev->sub_vendor_id, ~0);
>> @@ -2615,8 +2617,9 @@ 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_errno(errp, -EINVAL,
>> +                             "invalid PCI subsystem device ID provided");
>> +            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,
>> @@ -2646,7 +2649,8 @@ static int vfio_initfn(PCIDevice *pdev)
>>  
>>      ret = vfio_msix_early_setup(vdev);
>>      if (ret) {
>> -        return ret;
>> +        error_setg_errno(errp, ret, "msix early setup failure");
>> +        goto error;
>>      }
>>  
>>      vfio_bars_setup(vdev);
>> @@ -2669,9 +2673,9 @@ 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);
>> -            ret = -EINVAL;
>> +            error_setg_errno(errp, -EINVAL,
>> +                       "cannot support IGD OpRegion feature on hotplugged "
>> +                       "device");
>>              goto out_teardown;
>>          }
>>  
>> @@ -2679,16 +2683,15 @@ 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(errp, 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(errp, ret, "IGD OpRegion initialization 
>> failed");
>>              goto out_teardown;
>>          }
>>      }
>> @@ -2710,6 +2713,7 @@ static int vfio_initfn(PCIDevice *pdev)
>>          pci_device_set_intx_routing_notifier(&vdev->pdev, vfio_intx_update);
>>          ret = vfio_intx_enable(vdev);
>>          if (ret) {
>> +            error_setg_errno(errp, ret, "failed to enable intx");
>>              goto out_teardown;
>>          }
>>      }
>> @@ -2718,13 +2722,14 @@ 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);
>> -    return ret;
>> +error:
>> +    error_prepend(errp, "vfio: %s: ", vdev->vbasedev.name);
>>  }
>>  
>>  static void vfio_instance_finalize(Object *obj)
>> @@ -2853,7 +2858,7 @@ 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 4bb7690..14e3fc4 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 address@hidden"
>>  vfio_pci_reset(const char *name) " (%s)"
>>  vfio_pci_reset_flr(const char *name) "%s FLR/VFIO_DEVICE_RESET"
>