Re: [RFC] iommu: arm-smmu: stall support

From	Joerg Roedel <joro@8bytes.org>
Newsgroups	linux.kernel
Subject	Re: [RFC] iommu: arm-smmu: stall support
Date	2017-09-22 11:10 +0200
Message-ID	<uss8b-4hz-59@gated-at.bofh.it> (permalink)
References	<upIj7-Np-5@gated-at.bofh.it> <urpYJ-5sW-5@gated-at.bofh.it> <urrHc-6Af-15@gated-at.bofh.it>
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On Tue, Sep 19, 2017 at 10:23:43AM -0400, Rob Clark wrote:
> I would like to decide in the IRQ whether or not to queue work or not,
> because when we get a gpu fault, we tend to get 1000's of gpu faults
> all at once (and I really only need to handle the first one).  I
> suppose that could also be achieved by having a special return value
> from the fault handler to say "call me again from a wq"..
> 
> Note that in the drm driver I already have a suitable wq to queue the
> work, so it really doesn't buy me anything to have the iommu driver
> toss things off to a wq for me.  Might be a different situation for
> other drivers (but I guess mostly other drivers are using iommu API
> indirectly via dma-mapping?)

Okay, so since you are the only user for now, we don't need a
work-queue. But I still want the ->resume call-back to be hidden in the
iommu code and not be exposed to users.

We already have per-domain fault-handlers, so the best solution for now
is to call ->resume from report_iommu_fault() when the fault-handler
returns a special value.

Regards,

	Joerg

Thread

[RFC] iommu: arm-smmu: stall support Rob Clark <robdclark@gmail.com> - 2017-09-14 21:50 +0200
  Re: [RFC] iommu: arm-smmu: stall support Jean-Philippe Brucker <jean-philippe.brucker@arm.com> - 2017-09-18 13:20 +0200
    Re: [RFC] iommu: arm-smmu: stall support Rob Clark <robdclark@gmail.com> - 2017-09-18 14:20 +0200
      Re: [RFC] iommu: arm-smmu: stall support Will Deacon <will.deacon@arm.com> - 2017-09-18 19:40 +0200
  Re: [RFC] iommu: arm-smmu: stall support Joerg Roedel <joro@8bytes.org> - 2017-09-19 14:40 +0200
    Re: [RFC] iommu: arm-smmu: stall support Rob Clark <robdclark@gmail.com> - 2017-09-19 16:30 +0200
      Re: [RFC] iommu: arm-smmu: stall support Joerg Roedel <joro@8bytes.org> - 2017-09-22 11:10 +0200
        Re: [RFC] iommu: arm-smmu: stall support Jean-Philippe Brucker <jean-philippe.brucker@arm.com> - 2017-09-22 12:00 +0200
          Re: [RFC] iommu: arm-smmu: stall support Rob Clark <robdclark@gmail.com> - 2017-09-22 20:50 +0200

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