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Subject: Re: [PATCH v5 03/15] iommu/smmu: Report empty domain nesting info
To:     Liu Yi L <yi.l.liu@intel.com>, alex.williamson@redhat.com,
        baolu.lu@linux.intel.com, joro@8bytes.org
Cc:     kevin.tian@intel.com, jacob.jun.pan@linux.intel.com,
        ashok.raj@intel.com, jun.j.tian@intel.com, yi.y.sun@intel.com,
        jean-philippe@linaro.org, peterx@redhat.com, hao.wu@intel.com,
        stefanha@gmail.com, iommu@lists.linux-foundation.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>
References: <1594552870-55687-1-git-send-email-yi.l.liu@intel.com>
 <1594552870-55687-4-git-send-email-yi.l.liu@intel.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <5ee6b661-9c46-20ee-332a-1a449b6f3a43@redhat.com>
Date:   Fri, 17 Jul 2020 19:18:15 +0200
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Yi,

On 7/12/20 1:20 PM, 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.

you may add in the commit message you return an empty nesting info
struct for now as true nesting is not yet supported by the SMMUs.

Besides:
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> 
> Cc: Will Deacon <will@kernel.org>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Suggested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@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;
> +}
> +
>  static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>  				    enum iommu_attr attr, void *data)
>  {
> @@ -3028,8 +3054,7 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>  	case IOMMU_DOMAIN_UNMANAGED:
>  		switch (attr) {
>  		case DOMAIN_ATTR_NESTING:
> -			*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
> -			return 0;
> +			return arm_smmu_domain_nesting_info(smmu_domain, data);
>  		default:
>  			return -ENODEV;
>  		}
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 243bc4c..09e2f1b 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1506,6 +1506,32 @@ 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;
> +}
> +
>  static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>  				    enum iommu_attr attr, void *data)
>  {
> @@ -1515,8 +1541,7 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>  	case IOMMU_DOMAIN_UNMANAGED:
>  		switch (attr) {
>  		case DOMAIN_ATTR_NESTING:
> -			*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
> -			return 0;
> +			return arm_smmu_domain_nesting_info(smmu_domain, data);
>  		default:
>  			return -ENODEV;
>  		}
>