Re: [PATCH, RFC 03/62] mm/ksm: Do not merge pages with different KeyIDs

From: Kirill A. Shutemov
Date: Mon May 13 2019 - 10:29:18 EST

On Fri, May 10, 2019 at 06:07:11PM +0000, Dave Hansen wrote:
> On 5/8/19 7:43 AM, Kirill A. Shutemov wrote:
> > KeyID indicates what key to use to encrypt and decrypt page's content.
> > Depending on the implementation a cipher text may be tied to physical
> > address of the page. It means that pages with an identical plain text
> > would appear different if KSM would look at a cipher text. It effectively
> > disables KSM for encrypted pages.
> >
> > In addition, some implementations may not allow to read cipher text at all.
> >
> > KSM compares plain text instead (transparently to KSM code).
> >
> > But we still need to make sure that pages with identical plain text will
> > not be merged together if they are encrypted with different keys.
> >
> > To make it work kernel only allows merging pages with the same KeyID.
> > The approach guarantees that the merged page can be read by all users.
> I can't really parse this description. Can I suggest replacement text?


Kirill A. Shutemov