linux-kernel - Re: [PATCHv3 02/17] mm/khugepaged: Do not collapse pages in encrypted VMAs

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Message-ID: <f0e4648f-a458-856e-8a06-d186c280530a@intel.com>
Date:   Wed, 13 Jun 2018 10:50:24 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     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 02/17] mm/khugepaged: Do not collapse pages in encrypted
 VMAs

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?