linux-kernel - Re: [PATCH v2 1/4] x86/mm: Export force_dma

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Date:   Tue, 3 Sep 2019 08:14:51 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>, dri-devel@...ts.freedesktop.org,
        pv-drivers@...are.com, linux-graphics-maintainer@...are.com,
        linux-kernel@...r.kernel.org
Cc:     Thomas Hellstrom <thellstrom@...are.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH v2 1/4] x86/mm: Export force_dma_unencrypted

On 9/3/19 6:15 AM, Thomas Hellström (VMware) wrote:
> The force_dma_unencrypted symbol is needed by TTM to set up the correct
> page protection when memory encryption is active. Export it.

It would be great if this had enough background that I didn't have to
look at patch 4 to figure out what TTM might be.

Why is TTM special?  How many other drivers would have to be modified in
a one-off fashion if we go this way?  What's the logic behind this being
a non-GPL export?