Re: [PATCH] iommufd: fix returns ENOENT in iommufd_viommu_get_vdev_id()

[Pranjal Shrivastava <praan@google.com>]

On Mon, Aug 04, 2025 at 06:08:59PM +0800, Richard Gemego wrote:

Hi Richard, 
> In iommufd_viommu_get_vdev_id(), if viommu does not have any vdevs, fix
> this func to return 0 instead of ENOENT.
> 
> Fixes: ea94b211c548 ("iommufd/viommu: Add iommufd_viommu_get_vdev_id helper")
> Signed-off-by: Richard Gemego <richardgemego@gmail.com>
> Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
> ---
>  drivers/iommu/iommufd/driver.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
> index 922cd1fe7ec2..ad635af8555b 100644
> --- a/drivers/iommu/iommufd/driver.c
> +++ b/drivers/iommu/iommufd/driver.c
> @@ -68,6 +68,7 @@ int iommufd_viommu_get_vdev_id(struct iommufd_viommu *viommu,
>  			break;
>  		}
>  	}
> +	if (!index) 
> +		rc = 0;
>  	xa_unlock(&viommu->vdevs);
>  	return rc;
>  }

I'm afraid, I don't understand the motivation behind this? IIUC, if a 
dev is not associated to the vIOMMU -ENOENT is returned. This patch
seems to be returning 0 when the xarray is empty. The issue is that
returning 0, would indicate the caller that `*vdev_id` holds a valid 
value which doesn't seem to be the case here?

It seems the original behavior is correct. Nicolin/Jason am I missing
something here?

Thanks,
Praan.