From: "Tian, Kevin" <kevin.tian@intel.com>
To: Robin Murphy <robin.murphy@arm.com>, Nicolin Chen <nicolinc@nvidia.com>
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Subject: RE: [PATCH v2 3/5] vfio/iommu_type1: Remove the domain->ops comparison
Date: Thu, 23 Jun 2022 03:50:22 +0000 [thread overview]
Message-ID: <BN9PR11MB52760486306A90A208D7C6768CB59@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <6e1280c5-4b22-ebb3-3912-6c72bc169982@arm.com>
> From: Robin Murphy <robin.murphy@arm.com>
> Sent: Wednesday, June 22, 2022 3:55 PM
>
> On 2022-06-16 23:23, Nicolin Chen wrote:
> > On Thu, Jun 16, 2022 at 06:40:14AM +0000, Tian, Kevin wrote:
> >
> >>> 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. 😊
> >
> > Will edit this part. Thanks!
>
> Oh, physical platforms with mixed IOMMUs definitely exist already. The
> main point is that while bus_set_iommu still exists, the core code
> effectively *does* prevent multiple drivers from registering - even in
> emulated cases like the example above, virtio-iommu and VT-d would both
> try to bus_set_iommu(&pci_bus_type), and one of them will lose. The
> aspect which might warrant clarification is that there's no combination
> of supported drivers which claim non-overlapping buses *and* could
> appear in the same system - even if you tried to contrive something by
> emulating, say, VT-d (PCI) alongside rockchip-iommu (platform), you
> could still only describe one or the other due to ACPI vs. Devicetree.
>
This explanation is much clearer! thanks.
next prev parent reply other threads:[~2022-06-23 4:46 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-16 0:02 [PATCH v2 0/5] Simplify vfio_iommu_type1 attach/detach routine Nicolin Chen
2022-06-16 0:03 ` [PATCH v2 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group Nicolin Chen
2022-06-16 2:09 ` Baolu Lu
2022-06-16 2:40 ` Nicolin Chen
2022-06-16 6:28 ` Tian, Kevin
2022-06-16 0:03 ` [PATCH v2 2/5] vfio/iommu_type1: Prefer to reuse domains vs match enforced cache coherency Nicolin Chen
2022-06-16 6:29 ` Tian, Kevin
2022-06-21 22:46 ` Alex Williamson
2022-06-21 23:47 ` Nicolin Chen
2022-06-16 0:03 ` [PATCH v2 3/5] vfio/iommu_type1: Remove the domain->ops comparison Nicolin Chen
2022-06-16 6:40 ` Tian, Kevin
2022-06-16 22:23 ` Nicolin Chen
2022-06-22 7:54 ` Robin Murphy
2022-06-23 3:50 ` Tian, Kevin [this message]
2022-06-23 7:47 ` Nicolin Chen
2022-06-24 13:16 ` Jason Gunthorpe
2022-06-24 18:31 ` Robin Murphy
2022-06-24 18:46 ` Jason Gunthorpe
2022-06-16 0:03 ` [PATCH v2 4/5] vfio/iommu_type1: Clean up update_dirty_scope in detach_group() Nicolin Chen
2022-06-16 6:45 ` Tian, Kevin
2022-06-16 22:26 ` Nicolin Chen
2022-06-16 0:03 ` [PATCH v2 5/5] vfio/iommu_type1: Simplify group attachment Nicolin Chen
2022-06-16 7:08 ` Tian, Kevin
2022-06-16 22:40 ` Nicolin Chen
2022-06-17 2:53 ` Tian, Kevin
2022-06-17 23:07 ` Nicolin Chen
2022-06-20 4:03 ` Jason Gunthorpe
2022-06-21 20:59 ` Nicolin Chen
2022-06-20 10:11 ` Robin Murphy
2022-06-21 21:08 ` Nicolin Chen
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