Re: [PATCH 14/46] x86/sev, lto: Mark cpuid_table_copy as __visible_on_lto

[Peter Zijlstra]

On Mon, Nov 14, 2022 at 12:43:12PM +0100, Jiri Slaby (SUSE) wrote:
> From: Martin Liska <mliska@xxxxxxx>
> 
> 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 cpuid_table_copy as __visible_on_lto.
> 
> [js] use __visible_on_lto
> 
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Signed-off-by: Martin Liska <mliska@xxxxxxx>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> ---
>  arch/x86/kernel/sev-shared.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index 3a5b0c9c4fcc..554da8aabfc7 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -64,7 +64,7 @@ struct snp_cpuid_table {
>  static u16 ghcb_version __ro_after_init;
>  
>  /* Copy of the SNP firmware's CPUID page. */
> -static struct snp_cpuid_table cpuid_table_copy __ro_after_init;
> +__visible_on_lto struct snp_cpuid_table cpuid_table_copy __ro_after_init;

Same again, address is taken (and passed into inline asm). Must not be
eliminated.