Re: [RFC PATCH] iommu/arm-smmu-v3: Allow nested attach for PCI bridges without vDEVICE

Dmitry Malkin <[email protected]>
Newsgroups dev.linux.lists.iommu,dev.linux.lists.regressions,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-kernel,org.kernel.vger.stable
Message-ID <PA1P190MB255719949EC777E6D2DB2606DBA72@PA1P190MB2557.EURP190.PROD.OUTLOOK.COM> 
> This kind of situation is very challenging to setup in the VM, and at
> this point you may as well include the switch to the VM too.

Passing through the PCI switch would not help because the device without
a vDEVICE is the host Root Port. Neither the Root Port nor the switch
should be exposed to the VM.

A multi-device IOMMU group is an intentional effect of using
'pci=config_acs', and I would prefer to restore support for this
configuration upstream.

Dmitry
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