Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

[Li, ZhenHua]

Hi Dave,

There may be some possibilities that the old iommu data is corrupted by
some other modules. Currently we do not have a better solution for the
dmar faults.

But I think when this happens, we need to fix the module that corrupted
the old iommu data. I once met a similar problem in normal kernel, the
queue used by the qi_* functions was written again by another module.
The fix was in that module, not in iommu module.


Thanks
Zhenhua

On 04/03/2015 04:40 PM, Dave Young wrote:
> > To fix this problem, we modifies the behaviors of the intel vt-d in the
> > crashdump kernel:
> >
> > For DMA Remapping:
> > 1. To accept the vt-d hardware in an active state,
> > 2. Do not disable and re-enable the translation, keep it enabled.
> > 3. Use the old root entry table, do not rewrite the RTA register.
> > 4. Malloc and use new context entry table, copy data from the old ones that
> >     used by the old kernel.
>
> Have not read all the patches, but I have a question, not sure this has been
> answered before. Old memory is not reliable, what if the old memory get corrupted
> before panic? Is it safe to continue using it in 2nd kernel, I worry that it will
> cause problems.
>
> Hope I'm wrong though.
>
> Thanks
> Dave

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