On Wed, Jul 19, 2017 at 4:28 PM, Robin Murphy [off-list ref] wrote:

On 19/07/17 10:33, Anup Patel wrote:

quoted

Some of the IOMMUs (such as ARM SMMU) are capable of bypassing
transactions for which no IOMMU domain is configured.

This patch adds IOMMU_CAP_BYPASS which can be used by IOMMU
drivers to advertise transation bypass capability of an IOMMU.

Whatever the intended semantics of this are, I can't help thinking it
would be better served by allowing callers to explicitly allocate their
own IOMMU_DOMAIN_IDENTITY domains. That would also be useful for the
problem we have with legacy virtio devices behind real IOMMUs.

We want to use VFIO no-IOMMU mode for FlexRM device but
currently it does not allow on our SOC because IOMMU ops are
registered for platform bus.

Regards,
Anup