x86: Cleanup alternative_io() and friends, prep for asm_call()

[PATCH 16/20] x86/cpu: Use alternative_io() in amd_clear_divider()

Posted by Josh Poimboeuf 9 months, 1 week ago

Use the standard alternative_io() interface.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/processor.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b458ff0e4c79..d7f3f03594a2 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -709,8 +709,10 @@ static inline u32 per_cpu_l2c_id(unsigned int cpu)
  */
 static __always_inline void amd_clear_divider(void)
 {
-	asm volatile(ALTERNATIVE("", "div %[one]\n\t", X86_BUG_DIV0)
-		     :: "a" (0), "d" (0), [one] "r" (1));
+	alternative_io("",
+		       "div %[one]\n\t", X86_BUG_DIV0,
+		       ARG(),
+		       ARG("a" (0), "d" (0), [one] "r" (1)));
 }
 
 extern void amd_check_microcode(void);
-- 
2.48.1

Re: [PATCH 16/20] x86/cpu: Use alternative_io() in amd_clear_divider()

Posted by Uros Bizjak 9 months, 1 week ago

On Fri, Mar 14, 2025 at 10:42 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> Use the standard alternative_io() interface.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  arch/x86/include/asm/processor.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index b458ff0e4c79..d7f3f03594a2 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -709,8 +709,10 @@ static inline u32 per_cpu_l2c_id(unsigned int cpu)
>   */
>  static __always_inline void amd_clear_divider(void)
>  {
> -       asm volatile(ALTERNATIVE("", "div %[one]\n\t", X86_BUG_DIV0)
> -                    :: "a" (0), "d" (0), [one] "r" (1));
> +       alternative_io("",
> +                      "div %[one]\n\t", X86_BUG_DIV0,

A nit - can the above be in one line? Also no need for a trailing \n\t.

Thanks,
Uros.