Re: [Ksummit-discuss] [CORE TOPIC] Device error handling / reporting / isolation

[Daniel Vetter <daniel.vetter@ffwll.ch>]

On Mon, May 12, 2014 at 6:28 PM, Joerg Roedel <joro@8bytes.org> wrote:
> On Mon, May 12, 2014 at 09:16:11AM -0700, Andy Lutomirski wrote:
>> On Mon, May 12, 2014 at 8:35 AM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>> Just to check: are you talking about disabling the IOMMU if there's a
>> fault storm or disabling reporting of IOMMU faults?
>
> Probably about disabling the reporting of IOMMU faults. An IOMMU that is
> used for DMA-API mappings can not be disabled at runtime in a safe way.

I was actually thinking of fully disabling the IOMMU if it only has
one child device to isolate the possible damage. But maybe we need a
bit more clevernesss and a driver notifer. In drm/i915 we could use
that to declare the gpu wedged, which should be about the optimal
outcome:
- We can do that from any atomic context.
- It will stop userspace from submitting more commands, and userspace
falls back to software rendering if this happens.
- Kernel modeset should keep on working, increasing chances that the
user/developer can grab crucial information from the life system.

I think we'd need to play around with some real bugs to know what will
actually work.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch