Re: [RFC Part2 PATCH 04/30] x86/mm: split the physmap when adding the page in RMP table

[Borislav Petkov]

On Mon, Apr 19, 2021 at 12:46:53PM -0500, Brijesh Singh wrote:
> - KVM calls  alloc_page() to allocate a VMSA page. The allocator returns
> 0xffffc80000200000 (PFN 0x200, page-level=2M). The VMSA page is private
> page so KVM will call RMPUPDATE to add the page as a private page in the
> RMP table. While adding the RMP entry the KVM will use the page level=4K.

Right, and *here* we split the 2M page on the *host* so that there's no
discrepancy between the host pagetable and the RMP. I guess your patch
does exactly that. :)

And AFAIR, set_memory.c doesn't have the functionality to coalesce 4K
pages back into the corresponding 2M page. Which means, the RMP table is
in sync, more or less.

Thx and thanks for elaborating.

-- 
Regards/Gruss,
    Boris.

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