[RFC] iommu: arm-smmu: stall support

Hi Jean,

On Wed, Sep 27, 2017 at 02:49:00PM +0100, Jean-Philippe Brucker wrote:

I like this approach. When the device driver registers a fault handler,
it also tells when it would like to be called (either in atomic context,
blocking context, or both).

Is there a use-case for calling the same handler from both contexts?

enum iommu_fault_status {
        IOMMU_FAULT_STATUS_NONE = 0,
        IOMMU_FAULT_STATUS_FAILURE,
        IOMMU_FAULT_STATUS_INVALID,
        IOMMU_FAULT_STATUS_HANDLED,
        IOMMU_FAULT_STATUS_IGNORE,
};

This all certainly makes sense for the PRI/PASID case, but I don't think
that it makes sense yet to extend the existing report_iommu_fault()
interface to also handle PASID/PPR faults.

The later needs a lot more parameters to successfully handle a fault. In
the AMD driver these are all in 'struct fault', the relevant members
are:

        u64 address;
        u16 devid;
        u16 pasid;
        u16 tag;
        u16 finish;
        u16 flags;

And passing all this through the existing interface which also handles
non-pasid faults is cumbersome. So I'd like to keep the PASID/PPR
interface separate from the old one for now.

Regards,

	Joerg