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Subject: Re: [PATCHv3 03/17] mm/ksm: Do not merge pages with different KeyIDs
From: Dave Hansen <dave.hansen@intel.com>
References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com>
 <20180612143915.68065-4-kirill.shutemov@linux.intel.com>
 <63b7e88f-33d6-c5c1-f6cb-1bbb780e2cc4@intel.com>
 <20180613203108.k63fda4hvsqyczw7@black.fi.intel.com>
 <355d6b1f-9188-e93b-9cf1-01ece1879cad@intel.com>
Message-ID: <2fd62aa9-968d-c547-a509-dad3b28019ce@intel.com>
Date: Wed, 13 Jun 2018 13:40:48 -0700
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>, Tom Lendacky <thomas.lendacky@amd.com>, Kai Huang <kai.huang@linux.intel.com>, Jacob Pan <jacob.jun.pan@linux.intel.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

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.