linux-kernel - Re: [PATCH] Ability to read the MKTME status from userspace (patch v2)

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Message-ID: <b3ea365a-816c-b712-29c6-9f49df1bd41f@intel.com>
Date:   Thu, 25 Jun 2020 14:43:42 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Borislav Petkov <bp@...en8.de>,
        Daniel Gutson <daniel@...ypsium.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh@...nel.org>, Tony Luck <tony.luck@...el.com>,
        Rahul Tanwar <rahul.tanwar@...ux.intel.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Richard Hughes <hughsient@...il.com>
Subject: Re: [PATCH] Ability to read the MKTME status from userspace (patch
 v2)

On 6/25/20 2:39 PM, Andy Lutomirski wrote:
> What about MKTME platforms that (using hypothetical future kernel
> support) have encryption enabled for a node but have disabled it for
> specific pages using madvise()?  Or that have any other nontrivial
> policy like that?

I think it's fine if the magic new bit means "normal allocations get
hardware encryption".  If we have a way for users to opt out of that,
that's fine with me because the default is to provide it and a user must
have gone through _some_ hoop to undo the protection.

BTW, although the MKTME hardware and architecture support disabling
encryption, we don't have any plans to expose that to applications.