linux-kernel - Re: [RFC, PATCH 19/22] x86/mm: Implement free_encrypt

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Message-ID: <64d11e65-76b7-4e70-553c-009263b50a1c@intel.com>
Date:   Tue, 6 Mar 2018 05:52:44 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "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>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC, PATCH 19/22] x86/mm: Implement free_encrypt_page()

On 03/06/2018 12:54 AM, Kirill A. Shutemov wrote:
>> Have you measured how slow this is?
> No, I have not.

It would be handy to do this.  I *think* you can do it on normal
hardware, even if it does not have "real" support for memory encryption.
 Just don't set the encryption bits in the PTEs but go through all the
motions of cache flushing.

I think that will help tell us whether this is a really specialized
thing a la hugetlbfs or whether it's something we really want to support
as a first-class citizen in the VM.