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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Wed, 28 Sep 2022 18:39:57 +0200
Message-ID: <CANiq72m+3gfo=L4T7WY5MeSxZckQKeV+kVdvRhEAVtxcz9cC7g@mail.gmail.com>
Subject: Re: [PATCH v10 25/27] x86: enable initial Rust support
To:     Wei Liu <wei.liu@kernel.org>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, patches@lists.linux.dev,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        David Gow <davidgow@google.com>,
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        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>, linux-doc@vger.kernel.org
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On Wed, Sep 28, 2022 at 4:32 PM Wei Liu <wei.liu@kernel.org> wrote:
>
> I do wonder how many more things you will need to list here. As far as
> I can tell there is also other avx512* flags for the x86_64 target.

Yeah, there are a lot of target features, but they are not getting enabled.

Eventually, a stable target spec alternative (e.g. all relevant target
feature flags) should be available, and then we can know what the
guaranteed behavior will be and thus decide better which flags to keep
or not depending on how explicit we want to be with respect to that.

For the moment I went for consistency with the line above, since that
was enough to disable everything we needed, though as you may have
noticed, 3dnow and mmx are not there, because I had to move them back
to the target spec [1].

[1] https://github.com/Rust-for-Linux/linux/commit/c5eae3a6e69c63dc8d69f51f74f74b853831ec71

Cheers,
Miguel