linux-kernel - Re: [PATCHv3 03/17] mm/ksm: Do not merge pages with different KeyIDs

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Message-ID: <2fd62aa9-968d-c547-a509-dad3b28019ce@intel.com>
Date:   Wed, 13 Jun 2018 13:40:48 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv3 03/17] mm/ksm: Do not merge pages with different KeyIDs

On 06/13/2018 01:35 PM, 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?

/me goes back to look at the patch... which is doing exactly that

But, this still needs a stronger explanation of what goes wrong if this
patch is not in place.