Messages in this thread | | | From | "Kalra, Ashish" <> | Subject | RE: [PATCH Part2 v6 09/49] x86/fault: Add support to handle the RMP fault for user address | Date | Fri, 2 Sep 2022 15:33:20 +0000 |
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[AMD Official Use Only - General]
Hello Boris,
>> As I mentioned earlier, this is computing an index into a 4K page >> within a hugepage mapping, therefore, though pte_index() works for 2M >> pages, but pmd_index() will not work for 1G pages.
>Why not? What exactly do you need to get here?
>So the way I understand it is, you want to map the faulting address to a RMP entry. And that is either the 2M PMD entry when the page is a 1G one and the 4K PTE entry when the page is a 2M one?
>Why doesn't pmd_index() work?
Yes we want to map the faulting address to a RMP entry, but hugepage entries in RMP table are basically subpage 4K entries. So it is a 4K entry when the page is a 2M one and also a 4K entry when the page is a 1G one.
That's why the computation to get a 4K page index within a 2M/1G hugepage mapping is required.
>Also, why isn't the lookup function's signature:
>int snp_lookup_rmpentry(unsigned long address, int *level)
>and all that logic to do the conversion to a PFN also not in it?
Thanks, Ashish
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