linux-kernel - Re: [PATCH 12/46] x86/paravirt, lto: Mark native_steal_clock() as __visible_on

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Date:   Mon, 14 Nov 2022 16:58:27 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Martin Liska <mliska@...e.cz>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH 12/46] x86/paravirt, lto: Mark native_steal_clock() as
 __visible_on_lto

On Mon, Nov 14, 2022 at 12:43:10PM +0100, Jiri Slaby (SUSE) wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Symbols referenced from assembler (either directly or e.f. from
> DEFINE_STATIC_KEY()) need to be global and visible in gcc LTO because
> they could end up in a different object file than the assembler. This
> can lead to linker errors without this patch.

> @@ -120,7 +120,7 @@ unsigned int paravirt_patch(u8 type, void *insn_buff, unsigned long addr,
>  struct static_key paravirt_steal_enabled;
>  struct static_key paravirt_steal_rq_enabled;
>  
> -static u64 native_steal_clock(int cpu)
> +__visible_on_lto u64 native_steal_clock(int cpu)

More hate; same reason, DEFINE_STATIC_CALL() takes the function address
and stuffs it in a variable, WTF is GCC-LTO eliminating it?