linux-kernel - Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error

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Message-ID: <a438f99d-26a4-a1b5-9fc3-5abd2e76edb3@gmail.com>
Date:   Tue, 10 Nov 2020 10:44:14 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel
 compilation error

09.11.2020 10:25, Ard Biesheuvel пишет:
...
>>> So the options are
>>>
>>> a) merge my patch that adds 2 bytes of opcode to the Thumb2 build
>>> b) merge Dmitry's patch that adds an unconditional literal load to all builds
>>> c) remove kernel mode handling from vfp_support_entry() [my other patch]
>>> d) move sections around so that vfp_kmode_exception is guaranteed to
>>> be in range.
>>> e) do nothing
...
>> The performance argument is questionable to me, to be honest. In
>> practice the performance difference should be absolutely negligible for
>> either of the proposed options, it should stay in a noise even if
>> somebody thoroughly counting cycles, IMO.
>>
>> I'm still thinking that the best option will be to apply a).
>>
> 
> Can we take that as an acked-by?

Are you asking me for the ack? I think this is a more appropriate
question to Russel. I'm not arm/ maintainer, but could give r-b and t-b.

If you're going to follow approach that I'm suggesting with a) + d),
then could you please resend the two patches in a single series? The
first one-line patch-fix should contain the fixes tag.