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

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Date:   Tue, 6 Mar 2018 17:09:32 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...el.com>
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 Tue, Mar 06, 2018 at 05:52:44AM -0800, Dave Hansen wrote:
> 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.

Yes, allocation/freeing and KeyID interfaces can be tested with MKTME
support in hardware. I did most of my testing this way.

> 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.

I will benchmark this. But not right now.

-- 
 Kirill A. Shutemov