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

Li, ZhenHua
2015-04-03T09:02:39Z

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
>
>