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

[Duan, Zhenzhong]

>-----Original Message-----
>From: Eric Auger <eric.auger@redhat.com>
>Sent: Wednesday, September 27, 2023 3:36 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.
>
>you may add: no functional change intended

Will do.

>>
>> 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);
>hum looking at that again, I was confused by the fact we passed the name
>arg in
>
>vfio_attach_device() whereas vbasedev->name was already filled. Looking at pci
>vfio_realize()
>both are sometimes different
>
>    if (!qemu_uuid_is_null(&vdev->vf_token)) {
>        qemu_uuid_unparse(&vdev->vf_token, uuid);
>        name = g_strdup_printf("%s vf_token=%s", vbasedev->name, uuid);
>    } else {
>        name = g_strdup(vbasedev->name);
>    }
>This may be worth a doc comment.

Yes, agree this is confusing. Just want to ask about the doc comment?
Should I create a vfio doc or just a small comment on call site of 
vfio_attach_device()?

Thanks
Zhenzhong