linux-kernel - Re: [PATCH Part2 v6 09/49] x86/fault: Add support to handle the RMP fault for user address

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Message-ID: <YxGoBzOFT+sfwr4w@nazgul.tnic>
Date:   Fri, 2 Sep 2022 08:52:02 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kalra, Ashish" <Ashish.Kalra@....com>
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Subject: Re: [PATCH Part2 v6 09/49] x86/fault: Add support to handle the RMP
 fault for user address

On Thu, Sep 01, 2022 at 08:32:35PM +0000, Kalra, Ashish wrote:
> 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?

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?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette