linux-kernel - Re: [PATCH, RFC 44/62] x86/mm: Set KeyIDs in encrypted VMAs for MKTME

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Message-ID: <20190614114408.GD3436@hirez.programming.kicks-ass.net>
Date:   Fri, 14 Jun 2019 13:44:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC 44/62] x86/mm: Set KeyIDs in encrypted VMAs for MKTME

On Wed, May 08, 2019 at 05:44:04PM +0300, Kirill A. Shutemov wrote:
> From: Alison Schofield <alison.schofield@...el.com>
> 
> MKTME architecture requires the KeyID to be placed in PTE bits 51:46.
> To create an encrypted VMA, place the KeyID in the upper bits of
> vm_page_prot that matches the position of those PTE bits.
> 
> When the VMA is assigned a KeyID it is always considered a KeyID
> change. The VMA is either going from not encrypted to encrypted,
> or from encrypted with any KeyID to encrypted with any other KeyID.
> To make the change safely, remove the user pages held by the VMA
> and unlink the VMA's anonymous chain.

This does not look like a transformation that preserves content; is
mprotect() still a suitable name?