linux-kernel - Re: [PATCH v3 14/19] x86/coco: Make cc_set

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Date: Tue, 30 Jan 2024 15:16:09 -0800
From: Kevin Loughlin <kevinloughlin@...gle.com>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>, 
	Tom Lendacky <thomas.lendacky@....com>, Dionna Glaze <dionnaglaze@...gle.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, 
	Arnd Bergmann <arnd@...db.de>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>, linux-arch@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: Re: [PATCH v3 14/19] x86/coco: Make cc_set_mask() static inline

On Mon, Jan 29, 2024 at 10:06 AM Ard Biesheuvel <ardb+git@...gle.com> wrote:
>
> From: Ard Biesheuvel <ardb@...nel.org>
>
> Setting the cc_mask global variable may be done early in the boot while
> running fromm a 1:1 translation. This code is built with -fPIC in order
> to support this.
>
> Make cc_set_mask() static inline so it can execute safely in this
> context as well.
>
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>  arch/x86/coco/core.c        | 7 +------
>  arch/x86/include/asm/coco.h | 8 +++++++-
>  2 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
> index eeec9986570e..d07be9d05cd0 100644
> --- a/arch/x86/coco/core.c
> +++ b/arch/x86/coco/core.c
> @@ -14,7 +14,7 @@
>  #include <asm/processor.h>
>
>  enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
> -static u64 cc_mask __ro_after_init;
> +u64 cc_mask __ro_after_init;
>
>  static bool noinstr intel_cc_platform_has(enum cc_attr attr)
>  {
> @@ -148,8 +148,3 @@ u64 cc_mkdec(u64 val)
>         }
>  }
>  EXPORT_SYMBOL_GPL(cc_mkdec);
> -
> -__init void cc_set_mask(u64 mask)
> -{
> -       cc_mask = mask;
> -}
> diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
> index 6ae2d16a7613..ecc29d6136ad 100644
> --- a/arch/x86/include/asm/coco.h
> +++ b/arch/x86/include/asm/coco.h
> @@ -13,7 +13,13 @@ enum cc_vendor {
>  extern enum cc_vendor cc_vendor;
>
>  #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
> -void cc_set_mask(u64 mask);
> +static inline void cc_set_mask(u64 mask)

In the inline functions I changed/added to core.c in [0], I saw an
objtool warning on clang builds when using inline instead of
__always_inline; I did not see the same warning for gcc . Should we
similarly use __always_inline to strictly-enforce here?

[0] https://lore.kernel.org/lkml/20240130220845.1978329-2-kevinloughlin@google.com/#Z31arch:x86:coco:core.c