linux-kernel - Re: [PATCH 2/5] iommu: Add blocking_domain_ops field in iommu

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Message-ID: <YodVJ7ervpIdWfg+@8bytes.org>
Date:   Fri, 20 May 2022 10:45:27 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] iommu: Add blocking_domain_ops field in iommu_ops

On Mon, May 16, 2022 at 09:57:56AM +0800, Lu Baolu wrote:
>  	const struct iommu_domain_ops *default_domain_ops;
> +	const struct iommu_domain_ops *blocking_domain_ops;

I don't understand why extra domain-ops are needed for this. I think it
would be more straight-forward to implement allocation of
IOMMU_DOMAIN_BLOCKED domains in each driver and let the details be
handled in the set_dev() call-back. The IOMMU driver can make sure DMA
is blocked for a device when it encounters a IOMMU_DOMAIN_BLOCKED
domain.

For IOMMUs that have no explicit way to block DMA could just use an
unmanaged domain with an empty page-table.

Regards,

	Joerg