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Date:   Fri, 24 Mar 2023 13:30:14 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Eric Auger <eric.auger@redhat.com>
Cc:     Nicolin Chen <nicolinc@nvidia.com>, robin.murphy@arm.com,
        will@kernel.org, kevin.tian@intel.com, baolu.lu@linux.intel.com,
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        jean-philippe@linaro.org, linux-arm-kernel@lists.infradead.org,
        iommu@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED
 type of allocations
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On Fri, Mar 24, 2023 at 04:44:58PM +0100, Eric Auger wrote:

> Please can you explain the (use) case where !parent. This creates an
> unmanaged S1?

If parent is not specified then userspace can force the IOPTE format
to be S1 or S2 of a normal unmanaged domain.

Not sure there is a usecase, but it seems reasonable to support. It
would be useful if there is further parameterization of the S1 like
limiting the number of address bits or something.

Jason