linux-kernel - Re: [RFC PATCH] mm: extend memfd with ability to create "secret" memory areas

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Message-ID: <ab0a11ad5fde0cc71a725aac3ea81cc996e35bf1.camel@intel.com>
Date:   Tue, 11 Feb 2020 19:52:47 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "rppt@...nel.org" <rppt@...nel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "alan@...ux.intel.com" <alan@...ux.intel.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "willy@...radead.org" <willy@...radead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "cl@...ux.com" <cl@...ux.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        "tycho@...ho.ws" <tycho@...ho.ws>,
        "luto@...nel.org" <luto@...nel.org>,
        "kirill@...temov.name" <kirill@...temov.name>
Subject: Re: [RFC PATCH] mm: extend memfd with ability to create "secret"
 memory areas

On Sat, 2020-02-08 at 19:39 +0200, Mike Rapoport wrote:
> > Do we need to make kmap() work on these?
> 
> I don't think we need to make kmap() work on these. The idea is to prevent
> kernel from accessing such memory areas.

For the VM use case, KVM does kmap() guest memory when emulating page table
operations in some cases:
arch/x86/kvm/paging_tmpl.h:FNAME(cmpxchg_gpte).