Re: [PATCH v2 06/12] vfio/pci: Introduce vfio_[attach/detach]_device

[Eric Auger]

On 9/27/23 14:32, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Eric Auger <eric.auger@redhat.com>
>> Sent: Wednesday, September 27, 2023 8:23 PM
>> Subject: Re: [PATCH v2 06/12] vfio/pci: Introduce vfio_[attach/detach]_device
>>
>>
>>
>> On 9/27/23 12:07, Duan, Zhenzhong wrote:
>>> Hi Eric,
>>>
>>>> -----Original Message-----
>>>> From: Eric Auger <eric.auger@redhat.com>
>>>> Sent: Wednesday, September 27, 2023 5:02 PM
>>>> Subject: Re: [PATCH v2 06/12] vfio/pci: Introduce 
>>>> vfio_[attach/detach]_device
>>>>
>>>> Hi Zhenzhong,
>>>>
>>>> On 9/26/23 13:32, Zhenzhong Duan wrote:
>>>>> From: Eric Auger <eric.auger@redhat.com>
>>>>>
>>>>> We want the VFIO devices to be able to use two different
>>>>> IOMMU backends, the legacy VFIO one and the new iommufd one.
>>>>>
>>>>> Introduce vfio_[attach/detach]_device which aim at hiding the
>>>>> underlying IOMMU backend (IOCTLs, datatypes, ...).
>>>>>
>>>>> Once vfio_attach_device completes, the device is attached
>>>>> to a security context and its fd can be used. Conversely
>>>>> When vfio_detach_device completes, the device has been
>>>>> detached from the security context.
>>>>>
>>>>> At the moment only the implementation based on the legacy
>>>>> container/group exists. Let's use it from the vfio-pci device.
>>>>> Subsequent patches will handle other devices.
>>>>>
>>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>>>>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>>>>> ---
>>>>>  include/hw/vfio/vfio-common.h |  3 ++
>>>>>  hw/vfio/common.c              | 68 +++++++++++++++++++++++++++++++++++
>>>>>  hw/vfio/pci.c                 | 50 +++-----------------------
>>>>>  hw/vfio/trace-events          |  2 +-
>>>>>  4 files changed, 77 insertions(+), 46 deletions(-)
>>>>>
>>>>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-
>> common.h
>>>>> index c4e7c3b4a7..12fbfbc37d 100644
>>>>> --- a/include/hw/vfio/vfio-common.h
>>>>> +++ b/include/hw/vfio/vfio-common.h
>>>>> @@ -225,6 +225,9 @@ void vfio_put_group(VFIOGroup *group);
>>>>>  struct vfio_device_info *vfio_get_device_info(int fd);
>>>>>  int vfio_get_device(VFIOGroup *group, const char *name,
>>>>>                      VFIODevice *vbasedev, Error **errp);
>>>>> +int vfio_attach_device(char *name, VFIODevice *vbasedev,
>>>>> +                       AddressSpace *as, Error **errp);
>>>>> +void vfio_detach_device(VFIODevice *vbasedev);
>>>>>
>>>>>  int vfio_kvm_device_add_fd(int fd, Error **errp);
>>>>>  int vfio_kvm_device_del_fd(int fd, Error **errp);
>>>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>>>>> index 959b1362bb..7f3798b152 100644
>>>>> --- a/hw/vfio/common.c
>>>>> +++ b/hw/vfio/common.c
>>>>> @@ -2611,3 +2611,71 @@ int vfio_eeh_as_op(AddressSpace *as, uint32_t
>> op)
>>>>>      }
>>>>>      return vfio_eeh_container_op(container, op);
>>>>>  }
>>>>> +
>>>>> +static int vfio_device_groupid(VFIODevice *vbasedev, Error **errp)
>>>>> +{
>>>>> +    char *tmp, group_path[PATH_MAX], *group_name;
>>>>> +    int ret, groupid;
>>>>> +    ssize_t len;
>>>>> +
>>>>> +    tmp = g_strdup_printf("%s/iommu_group", vbasedev->sysfsdev);
>>>>> +    len = readlink(tmp, group_path, sizeof(group_path));
>>>>> +    g_free(tmp);
>>>>> +
>>>>> +    if (len <= 0 || len >= sizeof(group_path)) {
>>>>> +        ret = len < 0 ? -errno : -ENAMETOOLONG;
>>>>> +        error_setg_errno(errp, -ret, "no iommu_group found");
>>>>> +        return ret;
>>>>> +    }
>>>>> +
>>>>> +    group_path[len] = 0;
>>>>> +
>>>>> +    group_name = basename(group_path);
>>>>> +    if (sscanf(group_name, "%d", &groupid) != 1) {
>>>>> +        error_setg_errno(errp, errno, "failed to read %s", group_path);
>>>>> +        return -errno;
>>>>> +    }
>>>>> +    return groupid;
>>>>> +}
>>>>> +
>>>>> +int vfio_attach_device(char *name, VFIODevice *vbasedev,
>>>>> +                       AddressSpace *as, Error **errp)
>>>>> +{
>>>>> +    int groupid = vfio_device_groupid(vbasedev, errp);
>>>>> +    VFIODevice *vbasedev_iter;
>>>>> +    VFIOGroup *group;
>>>>> +    int ret;
>>>>> +
>>>>> +    if (groupid < 0) {
>>>>> +        return groupid;
>>>>> +    }
>>>>> +
>>>>> +    trace_vfio_attach_device(vbasedev->name, groupid);
>>>>> +
>>>>> +    group = vfio_get_group(groupid, as, errp);
>>>>> +    if (!group) {
>>>>> +        return -ENOENT;
>>>>> +    }
>>>>> +
>>>>> +    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
>>>>> +        if (strcmp(vbasedev_iter->name, vbasedev->name) == 0) {
>>>>> +            error_setg(errp, "device is already attached");
>>>>> +            vfio_put_group(group);
>>>>> +            return -EBUSY;
>>>>> +        }
>>>>> +    }
>>>>> +    ret = vfio_get_device(group, name, vbasedev, errp);
>>>>> +    if (ret) {
>>>>> +        vfio_put_group(group);
>>>>> +    }
>>>>> +
>>>>> +    return ret;
>>>>> +}
>>>>> +
>>>>> +void vfio_detach_device(VFIODevice *vbasedev)
>>>>> +{
>>>>> +    VFIOGroup *group = vbasedev->group;
>>>>> +
>>>>> +    vfio_put_base_device(vbasedev);
>>>>> +    vfio_put_group(group);
>>>>> +}
>>>>> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
>>>>> index 3b2ca3c24c..fe56789893 100644
>>>>> --- a/hw/vfio/pci.c
>>>>> +++ b/hw/vfio/pci.c
>>>>> @@ -2828,10 +2828,10 @@ static void vfio_populate_device(VFIOPCIDevice
>>>> *vdev, Error **errp)
>>>>>  static void vfio_put_device(VFIOPCIDevice *vdev)
>>>>>  {
>>>>> +    vfio_detach_device(&vdev->vbasedev);
>>>>> +
>>>>>      g_free(vdev->vbasedev.name);
>>>>>      g_free(vdev->msix);
>>>>> -
>>>>> -    vfio_put_base_device(&vdev->vbasedev);
>>>>>  }
>>>>>
>>>>>  static void vfio_err_notifier_handler(void *opaque)
>>>>> @@ -2978,13 +2978,9 @@ static void vfio_realize(PCIDevice *pdev, Error
>>>> **errp)
>>>>>  {
>>>>>      VFIOPCIDevice *vdev = VFIO_PCI(pdev);
>>>>>      VFIODevice *vbasedev = &vdev->vbasedev;
>>>>> -    VFIODevice *vbasedev_iter;
>>>>> -    VFIOGroup *group;
>>>>> -    char *tmp, *subsys, group_path[PATH_MAX], *group_name;
>>>>> +    char *tmp, *subsys;
>>>>>      Error *err = NULL;
>>>>> -    ssize_t len;
>>>>>      struct stat st;
>>>>> -    int groupid;
>>>>>      int i, ret;
>>>>>      bool is_mdev;
>>>>>      char uuid[UUID_FMT_LEN];
>>>>> @@ -3015,39 +3011,6 @@ static void vfio_realize(PCIDevice *pdev, Error
>>>> **errp)
>>>>>      vbasedev->type = VFIO_DEVICE_TYPE_PCI;
>>>>>      vbasedev->dev = DEVICE(vdev);
>>>>>
>>>>> -    tmp = g_strdup_printf("%s/iommu_group", vbasedev->sysfsdev);
>>>>> -    len = readlink(tmp, group_path, sizeof(group_path));
>>>>> -    g_free(tmp);
>>>>> -
>>>>> -    if (len <= 0 || len >= sizeof(group_path)) {
>>>>> -        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_setg_errno(errp, errno, "failed to read %s", group_path);
>>>>> -        goto error;
>>>>> -    }
>>>>> -
>>>>> -    trace_vfio_realize(vbasedev->name, groupid);
>>>>> -
>>>>> -    group = vfio_get_group(groupid, pci_device_iommu_address_space(pdev),
>>>> errp);
>>>>> -    if (!group) {
>>>>> -        goto error;
>>>>> -    }
>>>>> -
>>>>> -    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
>>>>> -        if (strcmp(vbasedev_iter->name, vbasedev->name) == 0) {
>>>>> -            error_setg(errp, "device is already attached");
>>>>> -            vfio_put_group(group);
>>>>> -            goto error;
>>>>> -        }
>>>>> -    }
>>>>> -
>>>>>      /*
>>>>>       * Mediated devices *might* operate compatibly with discarding of 
>>>>> RAM,
>> but
>>>>>       * we cannot know for certain, it depends on whether the mdev vendor
>>>> driver
>>>>> @@ -3065,7 +3028,6 @@ static void vfio_realize(PCIDevice *pdev, Error
>> **errp)
>>>>>      if (vbasedev->ram_block_discard_allowed && !is_mdev) {
>>>>>          error_setg(errp, "x-balloon-allowed only potentially compatible "
>>>>>                     "with mdev devices");
>>>>> -        vfio_put_group(group);
>>>>>          goto error;
>>>>>      }
>>>>>
>>>>> @@ -3076,10 +3038,10 @@ static void vfio_realize(PCIDevice *pdev, Error
>>>> **errp)
>>>>>          name = g_strdup(vbasedev->name);
>>>>>      }
>>>>>
>>>>> -    ret = vfio_get_device(group, name, vbasedev, errp);
>>>>> +    ret = vfio_attach_device(name, vbasedev,
>>>>> +                             pci_device_iommu_address_space(pdev), errp);
>>>>>      g_free(name);
>>>>>      if (ret) {
>>>>> -        vfio_put_group(group);
>>>> independently on this patch, I think in case of error we leak
>>>> vbasedev->name. Please have a look and if confirmed you can send a
>>>> separate patch.
>>> In case of error, vbasedev->name is freed in vfio_put_device().
>> called in vfio_instance_finalize only. See comment below
>>>> Also I think if any subsequent action fail we shoudl properly detach the
>>>> detach the device so introduce an extra error goto label, my bad sorry.
>>> vfio_detach_device is called in vfio_instance_finalize(), this is just to 
>>> follow
>>> the old code, group and container resource allocated in vfio_realize() are
>>> freed in vfio_instance_finalize().
>>>
>>> I agree this is strange, but I guess there may be some reason I'm unclear.
>> Yeah but if vfio_realize does fail, I am not sure the
>> vfio_instance_finalize gets called
> If vfio_realize fails, fio_exitfn() will not be called but 
> vfio_instance_finalize will.
> Note vfio_instance_finalize() is called by object_unref().
ah OK that's what I forgot then :-(

Eric
>
> Thanks
> Zhenzhong
>