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

[Markus Armbruster]

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.

* 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.

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.

> +                         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.

>      }
>  
>      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.

>  
>      /* 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"