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Reply-To: eric.auger@redhat.com
Subject: Re: [RFC 09/20] iommu: Add page size and address width attributes
To:     Liu Yi L <yi.l.liu@intel.com>, alex.williamson@redhat.com,
        jgg@nvidia.com, hch@lst.de, jasowang@redhat.com, joro@8bytes.org
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        lkml@metux.net, pbonzini@redhat.com, lushenming@huawei.com,
        corbet@lwn.net, ashok.raj@intel.com, yi.l.liu@linux.intel.com,
        jun.j.tian@intel.com, hao.wu@intel.com, dave.jiang@intel.com,
        jacob.jun.pan@linux.intel.com, kwankhede@nvidia.com,
        robin.murphy@arm.com, kvm@vger.kernel.org,
        iommu@lists.linux-foundation.org, dwmw2@infradead.org,
        linux-kernel@vger.kernel.org, baolu.lu@linux.intel.com,
        david@gibson.dropbear.id.au, nicolinc@nvidia.com
References: <20210919063848.1476776-1-yi.l.liu@intel.com>
 <20210919063848.1476776-10-yi.l.liu@intel.com>
From:   Eric Auger <eric.auger@redhat.com>
Message-ID: <e158380d-cb13-c1aa-6dd6-77032fe72106@redhat.com>
Date:   Wed, 22 Sep 2021 15:42:55 +0200
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Hi,

On 9/19/21 8:38 AM, Liu Yi L wrote:
> From: Lu Baolu <baolu.lu@linux.intel.com>
>
> This exposes PAGE_SIZE and ADDR_WIDTH attributes. The iommufd could use
> them to define the IOAS.
>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  include/linux/iommu.h | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 943de6897f56..86d34e4ce05e 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -153,9 +153,13 @@ enum iommu_dev_features {
>  /**
>   * enum iommu_devattr - Per device IOMMU attributes
>   * @IOMMU_DEV_INFO_FORCE_SNOOP [bool]: IOMMU can force DMA to be snooped.
> + * @IOMMU_DEV_INFO_PAGE_SIZE [u64]: Page sizes that iommu supports.
> + * @IOMMU_DEV_INFO_ADDR_WIDTH [u32]: Address width supported.
I think this deserves additional info. What address width do we talk
about, input, output, what stage if the IOMMU does support multiple stages

Thanks

Eric
>   */
>  enum iommu_devattr {
>  	IOMMU_DEV_INFO_FORCE_SNOOP,
> +	IOMMU_DEV_INFO_PAGE_SIZE,
> +	IOMMU_DEV_INFO_ADDR_WIDTH,
>  };
>  
>  #define IOMMU_PASID_INVALID	(-1U)