Re: [PATCH 1/5] iommu: Add capability IOMMU_CAP_BYPASS

[Anup Patel]

On Wed, Jul 19, 2017 at 4:28 PM, Robin Murphy <robin.murphy@xxxxxxx> wrote:
> On 19/07/17 10:33, Anup Patel wrote:
>> 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