On Wed, Jul 19, 2017 at 4:53 PM, Will Deacon [off-list ref] wrote:

On Wed, Jul 19, 2017 at 04:49:00PM +0530, Anup Patel wrote:

quoted

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

quoted

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.

Why do you want to use no-IOMMU mode if you have an IOMMU, and why you do
think the individual IOMMU drivers are the place to implement this?

NAK to the SMMU patches, for the reasons outlined by Robin.

We have limited number of SMRs on our SOC.

There are lot of devices for which we can potentially
configure SMMU but then due to limited number of
SMRs so we use SMMU only for certain devices.

For FlexRM device on our SOC, we don't intend to
use SMMU hence we need VFIO no-IOMMU mode
working for FlexRM device on our SOC.

Please re-consider your NAK.

Regards,
Anup