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Date: Wed, 13 Jun 2018 23:18:02 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv3 02/17] mm/khugepaged: Do not collapse pages in
 encrypted VMAs
Message-ID: <20180613201802.45m2745soztmkxmp@black.fi.intel.com>
References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com>
 <20180612143915.68065-3-kirill.shutemov@linux.intel.com>
 <f0e4648f-a458-856e-8a06-d186c280530a@intel.com>
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To: Dave Hansen <dave.hansen@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 Wed, Jun 13, 2018 at 05:50:24PM +0000, Dave Hansen wrote:
> On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> > Pages for encrypted VMAs have to be allocated in a special way:
> > we would need to propagate down not only desired NUMA node but also
> > whether the page is encrypted.
> > 
> > It complicates not-so-trivial routine of huge page allocation in
> > khugepaged even more. It also puts more pressure on page allocator:
> > we cannot re-use pages allocated for encrypted VMA to collapse
> > page in unencrypted one or vice versa.
> > 
> > I think for now it worth skipping encrypted VMAs. We can return
> > to this topic later.
> 
> You're asking for this to be included, but without a major piece of THP
> support.  Is THP support unimportant for this feature?
> 
> Are we really asking the x86 maintainers to merge this feature with this
> restriction in place?

I gave it more thought after your comment and I think I see a way to get
khugepaged work with memory encryption.

Let me check it tomorrow.

-- 
 Kirill A. Shutemov