linux-kernel - Re: [PATCH v6 09/17] x86/static_call: Add out-of-line static call implementation

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Message-ID: <20200710181331.1ad69ef6@oasis.local.home>
Date:   Fri, 10 Jul 2020 18:13:31 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        bristot@...hat.com, jbaron@...mai.com,
        torvalds@...ux-foundation.org, tglx@...utronix.de,
        mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, jpoimboe@...hat.com,
        pbonzini@...hat.com, mathieu.desnoyers@...icios.com,
        linux@...musvillemoes.dk
Subject: Re: [PATCH v6 09/17] x86/static_call: Add out-of-line static call
 implementation

On Fri, 10 Jul 2020 15:38:40 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> From: Josh Poimboeuf <jpoimboe@...hat.com>
> 
> Add the x86 out-of-line static call implementation.  For each key, a
> permanent trampoline is created which is the destination for all static
> calls for the given key.  The trampoline has a direct jump which gets
> patched by static_call_update() when the destination function changes.

FYI, I get the following warnings after applying this patch.

/work/git/linux-test.git/arch/x86/kernel/static_call.c: In function ‘__static_call_transform’:
/work/git/linux-test.git/arch/x86/kernel/static_call.c:9:43: warning: passing argument 2 of ‘text_gen_insn’ makes pointer from integer without a cast [-Wint-conversion]
    9 |  const void *code = text_gen_insn(opcode, (long)insn, (long)func);
      |                                           ^~~~~~~~~~
      |                                           |
      |                                           long int
In file included from /work/git/linux-test.git/arch/x86/include/asm/static_call.h:5,
                 from /work/git/linux-test.git/include/linux/static_call.h:62,
                 from /work/git/linux-test.git/arch/x86/kernel/static_call.c:2:
/work/git/linux-test.git/arch/x86/include/asm/text-patching.h:95:44: note: expected ‘const void *’ but argument is of type ‘long int’
   95 | void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
      |                                ~~~~~~~~~~~~^~~~
/work/git/linux-test.git/arch/x86/kernel/static_call.c:9:55: warning: passing argument 3 of ‘text_gen_insn’ makes pointer from integer without a cast [-Wint-conversion]
    9 |  const void *code = text_gen_insn(opcode, (long)insn, (long)func);
      |                                                       ^~~~~~~~~~
      |                                                       |
      |                                                       long int
In file included from /work/git/linux-test.git/arch/x86/include/asm/static_call.h:5,
                 from /work/git/linux-test.git/include/linux/static_call.h:62,
                 from /work/git/linux-test.git/arch/x86/kernel/static_call.c:2:
/work/git/linux-test.git/arch/x86/include/asm/text-patching.h:95:62: note: expected ‘const void *’ but argument is of type ‘long int’
   95 | void *text_gen_insn(u8 opcode, const void *addr, const void *dest)


-- Steve