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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 19 Apr 2021 11:50:52 -0700
Message-ID: <CAHk-=wiqX=uweoE+4hUTSLRsR87u2WAnYjmQtR1Zw0k0-cMocA@mail.gmail.com>
Subject: Re: [PATCH 00/13] [RFC] Rust support
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Wedson Almeida Filho <wedsonaf@google.com>, ojeda@kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Will Deacon <will@kernel.org>
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On Mon, Apr 19, 2021 at 11:38 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> It changes it for the worse, in that access to fields that are shared
> across threads *must* either use atomic types

Well, we won't be using those broken types in the core kernel, so that
would all be entirely on the Rust side.

And I don't expect the Rust side to do a lot of non-locked accesses,
which presumably shouldn't need any of this anyway.

If Rust code ends up accessing actual real kernel data structures with
memory ordering, then that will be to types that do *not* follow the
useless C++ atomics, and that in turn presumably means that it will be
done as "unsafe" helpers that do what the LKMM does (ie READ_ONCE()
and all the rest of it).

                 Linus