linux-kernel - RE: [PATCH v2 3/5] vfio/iommu_type1: Remove the domain->ops comparison

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Date:   Thu, 16 Jun 2022 06:40:14 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
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Subject: RE: [PATCH v2 3/5] vfio/iommu_type1: Remove the domain->ops
 comparison

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Thursday, June 16, 2022 8:03 AM
> 
> The domain->ops validation was added, as a precaution, for mixed-driver
> systems. However, at this moment only one iommu driver is possible. So
> remove it.

It's true on a physical platform. But I'm not sure whether a virtual platform
is allowed to include multiple e.g. one virtio-iommu alongside a virtual VT-d
or a virtual smmu. It might be clearer to claim that (as Robin pointed out)
there is plenty more significant problems than this to solve instead of simply
saying that only one iommu driver is possible if we don't have explicit code
to reject such configuration. 😊

> 
> Per discussion with Robin, in future when many can be permitted we will
> rely on the IOMMU core code to check the domain->ops:
> https://lore.kernel.org/linux-iommu/6575de6d-94ba-c427-5b1e-
> 967750ddff23@....com/
> 
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>

Apart from that,

Reviewed-by: Kevin Tian <kevin.tian@...el.com>