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 <PA1P190MB25573D7CFE42EF7DD2A8CDE8DBDA2@PA1P190MB2557.EURP190.PROD.OUTLOOK.COM> 
Hi Jason,

> If viommu should support multi-device groups, I'm not sure. I want to
> know why you even have multi-device groups in the first place because
> that is not normal at all.

That is because of the 'pci=config_acs' kernel command-line parameter. This causes the kernel to create a single IOMMU group containing multiple PCIe devices, including the bridge (PCIe Root Port).

Dmitry
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