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

[Duan, Zhenzhong]

>-----Original Message-----
>From: Cédric Le Goater <clg@redhat.com>
>Sent: Wednesday, September 27, 2023 6:17 PM
>Subject: Re: [PATCH v2 06/12] vfio/pci: Introduce vfio_[attach/detach]_device
>
>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);
>>           goto error;
>>       }
>>
>> @@ -3304,7 +3266,6 @@ error:
>>   static void vfio_instance_finalize(Object *obj)
>>   {
>>       VFIOPCIDevice *vdev = VFIO_PCI(obj);
>> -    VFIOGroup *group = vdev->vbasedev.group;
>>
>>       vfio_display_finalize(vdev);
>>       vfio_bars_finalize(vdev);
>> @@ -3318,7 +3279,6 @@ static void vfio_instance_finalize(Object *obj)
>>        * g_free(vdev->igd_opregion);
>>        */
>>       vfio_put_device(vdev);
>
>Please rebase v2 on vfio-next. I merged your patch since :)

Sure, will do. Maybe will be a little late. We will have national holiday 
between Sep 29 and Oct 6.

Thanks
Zhenzhong