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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Mon, 5 Nov 2018 09:52:52 +0100
Message-ID: <CAK8P3a2c98VVPArCkdAR=-nnDBq1gYRCLDDgQB71eGiTSRdb4A@mail.gmail.com>
Subject: Re: [RFC 0/2] RISC-V: A proposal to add vendor-specific code
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Vincent Chen <vincentc@andestech.com>, aou@eecs.berkeley.edu,
        alankao@andestech.com, greentime@andestech.com, palmer@sifive.com,
        linux-kernel@vger.kernel.org, zong@andestech.com,
        kito@andestech.com, linux-riscv@lists.infradead.org,
        deanbo422@gmail.com
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On 11/5/18, Christoph Hellwig <hch@infradead.org> wrote:
> On Mon, Nov 05, 2018 at 02:58:07PM +0800, Vincent Chen wrote:
>> Many thanks for kinds of comments. I quickly synthesize the comments and
>> list them as below.
>> 1. The kernel image shall include all vendor-specific code.
>
> I fundamentally disagree with this=E2=80=A6 and think it should be the co=
ntrary.
>
> 1. The kernel shall support no vendor specific instructions whatsoever,
> period.

I think what was meant above is

1. If a vendor extension requires kernel support, that support
must be able to be built into a kernel image without breaking support
for CPUs that do not have that extension, to allow building a single
kernel image that works on all CPUs.

       Arnd