Re: [PATCH v6 13/21] vfio/platform: Make vfio cdev pre-openable by passing a file handle

[Cédric Le Goater]

On 11/14/23 11:09, Zhenzhong Duan wrote:
> This gives management tools like libvirt a chance to open the vfio
> cdev with privilege and pass FD to qemu. This way qemu never needs
> to have privilege to open a VFIO or iommu cdev node.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>

Reviewed-by: Cédric Le Goater <clg@redhat.com>

Thanks,

C.


> ---
>   hw/vfio/platform.c | 32 ++++++++++++++++++++++++--------
>   1 file changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
> index 98ae4bc655..a97d9c6234 100644
> --- a/hw/vfio/platform.c
> +++ b/hw/vfio/platform.c
> @@ -531,14 +531,13 @@ static VFIODeviceOps vfio_platform_ops = {
>    */
>   static int vfio_base_device_init(VFIODevice *vbasedev, Error **errp)
>   {
> -    struct stat st;
>       int ret;
>   
> -    /* @sysfsdev takes precedence over @host */
> -    if (vbasedev->sysfsdev) {
> +    /* @fd takes precedence over @sysfsdev which takes precedence over @host */
> +    if (vbasedev->fd < 0 && vbasedev->sysfsdev) {
>           g_free(vbasedev->name);
>           vbasedev->name = g_path_get_basename(vbasedev->sysfsdev);
> -    } else {
> +    } else if (vbasedev->fd < 0) {
>           if (!vbasedev->name || strchr(vbasedev->name, '/')) {
>               error_setg(errp, "wrong host device name");
>               return -EINVAL;
> @@ -548,10 +547,9 @@ static int vfio_base_device_init(VFIODevice *vbasedev, 
> Error **errp)
>                                                vbasedev->name);
>       }
>   
> -    if (stat(vbasedev->sysfsdev, &st) < 0) {
> -        error_setg_errno(errp, errno,
> -                         "failed to get the sysfs host device file status");
> -        return -errno;
> +    ret = vfio_device_get_name(vbasedev, errp);
> +    if (ret) {
> +        return ret;
>       }
>   
>       ret = vfio_attach_device(vbasedev->name, vbasedev,
> @@ -658,6 +656,20 @@ static Property vfio_platform_dev_properties[] = {
>       DEFINE_PROP_END_OF_LIST(),
>   };
>   
> +static void vfio_platform_instance_init(Object *obj)
> +{
> +    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(obj);
> +
> +    vdev->vbasedev.fd = -1;
> +}
> +
> +#ifdef CONFIG_IOMMUFD
> +static void vfio_platform_set_fd(Object *obj, const char *str, Error **errp)
> +{
> +    vfio_device_set_fd(&VFIO_PLATFORM_DEVICE(obj)->vbasedev, str, errp);
> +}
> +#endif
> +
>   static void vfio_platform_class_init(ObjectClass *klass, void *data)
>   {
>       DeviceClass *dc = DEVICE_CLASS(klass);
> @@ -665,6 +677,9 @@ static void vfio_platform_class_init(ObjectClass *klass, 
> void *data)
>   
>       dc->realize = vfio_platform_realize;
>       device_class_set_props(dc, vfio_platform_dev_properties);
> +#ifdef CONFIG_IOMMUFD
> +    object_class_property_add_str(klass, "fd", NULL, vfio_platform_set_fd);
> +#endif
>       dc->vmsd = &vfio_platform_vmstate;
>       dc->desc = "VFIO-based platform device assignment";
>       sbc->connect_irq_notifier = vfio_start_irqfd_injection;
> @@ -677,6 +692,7 @@ static const TypeInfo vfio_platform_dev_info = {
>       .name = TYPE_VFIO_PLATFORM,
>       .parent = TYPE_SYS_BUS_DEVICE,
>       .instance_size = sizeof(VFIOPlatformDevice),
> +    .instance_init = vfio_platform_instance_init,
>       .class_init = vfio_platform_class_init,
>       .class_size = sizeof(VFIOPlatformDeviceClass),
>   };