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Subject: Re: [PATCHv3 02/17] mm/khugepaged: Do not collapse pages in encrypted
 VMAs
References: <20180612143915.68065-1-kirill.shutemov@linux.intel.com>
 <20180612143915.68065-3-kirill.shutemov@linux.intel.com>
From: Dave Hansen <dave.hansen@intel.com>
Message-ID: <f0e4648f-a458-856e-8a06-d186c280530a@intel.com>
Date: Wed, 13 Jun 2018 10:50:24 -0700
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, 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>
Cc: 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 06/12/2018 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?