linux-kernel - Re: [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do encryption

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Date:   Tue, 7 Dec 2021 11:52:54 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Martin Fernandez <martin.fernandez@...ypsium.com>,
        Mike Rapoport <rppt@...nel.org>
Cc:     Richard Hughes <hughsient@...il.com>, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-mm@...ck.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, ardb@...nel.org, dvhart@...radead.org,
        andy@...radead.org, gregkh@...uxfoundation.org, rafael@...nel.org,
        akpm@...ux-foundation.org, daniel.gutson@...ypsium.com,
        alex.bazhaniuk@...ypsium.com, alison.schofield@...el.com
Subject: Re: [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do
 encryption

On 12/7/21 11:45 AM, Martin Fernandez wrote:
>> I wonder, for example, why did you choose per-node reporting rather than
>> per-region as described in UEFI spec.
> Some time ago we discussed about this and concluded with Dave Hansen
> that it was better to do it in this per-node way.

Physical memory regions aren't exposed to userspace in any meaningful way.

An ABI that says "everything is encrypted" is pretty meaningless and
only useful for this one, special case.

A per-node ABI is useful for this case and is also useful going forward
if folks want to target allocations from applications to NUMA nodes
which have encryption capabilities.  The ABI in this set is useful for
the immediate case and is useful to other folks.