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Date:   Wed, 13 Jun 2018 23:41:34 +0300
From:   "Kirill A. Shutemov" <>
To:     Dave Hansen <>
Cc:     Ingo Molnar <>,,
        Thomas Gleixner <>,
        "H. Peter Anvin" <>,
        Tom Lendacky <>,
        Kai Huang <>,
        Jacob Pan <>,,
Subject: Re: [PATCHv3 03/17] mm/ksm: Do not merge pages with different KeyIDs

On Wed, Jun 13, 2018 at 08:35:46PM +0000, Dave Hansen wrote:
> On 06/13/2018 01:31 PM, Kirill A. Shutemov wrote:
> >> What actually happens without this patch in place?
> > 
> > One of processes would get the page mapped with wrong KeyID and see
> > garbage. 
> OK, but what about two pages with the same KeyID?  It's actually totally
> possible for KSM to determine that two pages have the same plaintext and
> merge them.  Why don't we do that?

That's exactly what we do :)

> > We setup mapping according to KeyID in vma->vm_page_prot.
> Then why do we bother with page_keyid() and the page_ext stuff?

VMA is not always around.

Using KeyID in vma->vm_page_prot we don't need to change anything in PTE
setup functions. It just works.

 Kirill A. Shutemov

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