linux-kernel - Re: [PATCHv2 06/14] mm/page_alloc: Propagate encryption KeyID through page allocator

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Message-ID: <20180329125227.GF31039@dhcp22.suse.cz>
Date:   Thu, 29 Mar 2018 14:52:27 +0200
From:   Michal Hocko <mhocko@...nel.org>
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>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv2 06/14] mm/page_alloc: Propagate encryption KeyID
 through page allocator

On Thu 29-03-18 15:37:12, Kirill A. Shutemov wrote:
> On Thu, Mar 29, 2018 at 01:20:34PM +0200, Michal Hocko wrote:
> > On Wed 28-03-18 19:55:32, Kirill A. Shutemov wrote:
> > > Modify several page allocation routines to pass down encryption KeyID to
> > > be used for the allocated page.
> > > 
> > > There are two basic use cases:
> > > 
> > >  - alloc_page_vma() use VMA's KeyID to allocate the page.
> > > 
> > >  - Page migration and NUMA balancing path use KeyID of original page as
> > >    KeyID for newly allocated page.
> > 
> > I am sorry but I am out of time to look closer but this just raised my
> > eyebrows. This looks like a no-go. The basic allocator has no business
> > in fancy stuff like a encryption key. If you need something like that
> > then just build a special allocator API on top. This looks like a no-go
> > to me.
> 
> The goal is to make memory encryption first class citizen in memory
> management and not to invent parallel subsysustem (as we did with hugetlb).

How do you get a page_keyid for random kernel allocation?
 
> Making memory encryption integral part of Linux VM would involve handing
> encrypted page everywhere we expect anonymous page to appear.

How many architectures will implement this feature?
-- 
Michal Hocko
SUSE Labs