On Sun, Jul 12, 2020 at 04:20:58AM -0700, Liu Yi L wrote:
> This patch is added as instead of returning a boolean for DOMAIN_ATTR_NESTING,
> iommu_domain_get_attr() should return an iommu_nesting_info handle.
> 
> Cc: Will Deacon <w...@kernel.org>
> Cc: Robin Murphy <robin.mur...@arm.com>
> Cc: Eric Auger <eric.au...@redhat.com>
> Cc: Jean-Philippe Brucker <jean-phili...@linaro.org>
> Suggested-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
> Signed-off-by: Liu Yi L <yi.l....@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun....@linux.intel.com>
> ---
> v4 -> v5:
> *) address comments from Eric Auger.
> ---
>  drivers/iommu/arm-smmu-v3.c | 29 +++++++++++++++++++++++++++--
>  drivers/iommu/arm-smmu.c    | 29 +++++++++++++++++++++++++++--
>  2 files changed, 54 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index f578677..ec815d7 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -3019,6 +3019,32 @@ static struct iommu_group 
> *arm_smmu_device_group(struct device *dev)
>       return group;
>  }
>  
> +static int arm_smmu_domain_nesting_info(struct arm_smmu_domain *smmu_domain,
> +                                     void *data)
> +{
> +     struct iommu_nesting_info *info = (struct iommu_nesting_info *)data;
> +     unsigned int size;
> +
> +     if (!info || smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
> +             return -ENODEV;
> +
> +     size = sizeof(struct iommu_nesting_info);
> +
> +     /*
> +      * if provided buffer size is smaller than expected, should
> +      * return 0 and also the expected buffer size to caller.
> +      */
> +     if (info->size < size) {
> +             info->size = size;
> +             return 0;
> +     }
> +
> +     /* report an empty iommu_nesting_info for now */
> +     memset(info, 0x0, size);
> +     info->size = size;
> +     return 0;
> +}

Have you verified that this doesn't break the existing usage of
DOMAIN_ATTR_NESTING in drivers/vfio/vfio_iommu_type1.c?

Will
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