From: Andi Kleen <ak@linux.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.

So mark native_steal_clock() as __visible_on_lto.

[js] use __visible_on_lto

Cc: Juergen Gross <jgross@suse.com>
Cc: "Srivatsa S. Bhat
Cc: Alexey Makhalov <amakhalov@vmware.com>
Cc: VMware PV-Drivers Reviewers <pv-drivers@vmware.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Martin Liska <mliska@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 arch/x86/kernel/paravirt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 7ca2d46c08cc..27a537cd4b0e 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -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)
 {
 	return 0;
 }
-- 
2.38.1

On Mon, Nov 14, 2022 at 12:43:10PM +0100, Jiri Slaby (SUSE) wrote:
> From: Andi Kleen <ak@linux.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?