From mboxrd@z Thu Jan  1 00:00:00 1970
From: joro@8bytes.org (Joerg Roedel)
Date: Wed, 27 Sep 2017 16:35:34 +0200
Subject: [RFC] iommu: arm-smmu: stall support
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 <32e3ab2c-a996-c805-2a0d-a2e85deb3a50@arm.com>
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Message-ID: <20170927143534.GQ8398@8bytes.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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