Messages in this thread | | | Date | Tue, 19 Aug 2014 13:02:39 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH 1/1] iommu/vt-d : clear old root entry for dump kernel |
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On Mon, Aug 18, 2014 at 11:27:01PM +0000, Li, Zhen-Hua wrote: > : [fault reason 01] Present bit in root entry is clear > It appears when iommu initializing in the kdump kernel.
Hmm, do you have an explanation how this can happen? From how I read the code, the kdump kernel disables translation on the IOMMU, then sets a new root entry, and then re-enabled translation. To me it looks like there is no point in time where translation is enabled and the root-entry is clear (present-bit==0).
But obviously I am missing something if you see the message above.
Btw, have you looked into this patch-set posted earlier this year:
https://lkml.org/lkml/2014/4/24/836
It approaches the same problem-space, but also cares about in-flight DMA.
Joerg
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