In line with WBINVD usage, add WBONINVD helper functions. For the
wbnoinvd() helper, fall back to WBINVD if X86_FEATURE_WBNOINVD is not
present.

Signed-off-by: Kevin Loughlin <kevinloughlin@google.com>
---
 arch/x86/include/asm/smp.h           |  7 +++++++
 arch/x86/include/asm/special_insns.h | 15 ++++++++++++++-
 arch/x86/lib/cache-smp.c             | 12 ++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index ca073f40698f..ecf93a243b83 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -112,6 +112,7 @@ void native_play_dead(void);
 void play_dead_common(void);
 void wbinvd_on_cpu(int cpu);
 int wbinvd_on_all_cpus(void);
+int wbnoinvd_on_all_cpus(void);
 
 void smp_kick_mwait_play_dead(void);
 
@@ -160,6 +161,12 @@ static inline int wbinvd_on_all_cpus(void)
 	return 0;
 }
 
+static inline int wbnoinvd_on_all_cpus(void)
+{
+	wbnoinvd();
+	return 0;
+}
+
 static inline struct cpumask *cpu_llc_shared_mask(int cpu)
 {
 	return (struct cpumask *)cpumask_of(0);
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 03e7c2d49559..94640c3491d7 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -117,7 +117,20 @@ static inline void wrpkru(u32 pkru)
 
 static __always_inline void wbinvd(void)
 {
-	asm volatile("wbinvd": : :"memory");
+	asm volatile("wbinvd" : : : "memory");
+}
+
+/*
+ * Cheaper version of wbinvd(). Call when caches
+ * need to be written back but not invalidated.
+ */
+static __always_inline void wbnoinvd(void)
+{
+	/*
+	 * Use the compatible but more destructive "invalidate"
+	 * variant when no-invalidate is unavailable.
+	 */
+	alternative("wbinvd", "wbnoinvd", X86_FEATURE_WBNOINVD);
 }
 
 static inline unsigned long __read_cr4(void)
diff --git a/arch/x86/lib/cache-smp.c b/arch/x86/lib/cache-smp.c
index 7af743bd3b13..7ac5cca53031 100644
--- a/arch/x86/lib/cache-smp.c
+++ b/arch/x86/lib/cache-smp.c
@@ -20,3 +20,15 @@ int wbinvd_on_all_cpus(void)
 	return 0;
 }
 EXPORT_SYMBOL(wbinvd_on_all_cpus);
+
+static void __wbnoinvd(void *dummy)
+{
+	wbnoinvd();
+}
+
+int wbnoinvd_on_all_cpus(void)
+{
+	on_each_cpu(__wbnoinvd, NULL, 1);
+	return 0;
+}
+EXPORT_SYMBOL(wbnoinvd_on_all_cpus);
-- 
2.48.1.262.g85cc9f2d1e-goog

On Wed, Jan 22, 2025 at 01:34:37AM +0000, Kevin Loughlin wrote:
> In line with WBINVD usage, add WBONINVD helper functions. For the
> wbnoinvd() helper, fall back to WBINVD if X86_FEATURE_WBNOINVD is not
> present.
> 
> Signed-off-by: Kevin Loughlin <kevinloughlin@google.com>
> ---
>  arch/x86/include/asm/smp.h           |  7 +++++++
>  arch/x86/include/asm/special_insns.h | 15 ++++++++++++++-
>  arch/x86/lib/cache-smp.c             | 12 ++++++++++++
>  3 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index ca073f40698f..ecf93a243b83 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -112,6 +112,7 @@ void native_play_dead(void);
>  void play_dead_common(void);
>  void wbinvd_on_cpu(int cpu);
>  int wbinvd_on_all_cpus(void);
> +int wbnoinvd_on_all_cpus(void);
>  
>  void smp_kick_mwait_play_dead(void);
>  
> @@ -160,6 +161,12 @@ static inline int wbinvd_on_all_cpus(void)
>  	return 0;
>  }
>  
> +static inline int wbnoinvd_on_all_cpus(void)
> +{
> +	wbnoinvd();
> +	return 0;
> +}
> +
>  static inline struct cpumask *cpu_llc_shared_mask(int cpu)
>  {
>  	return (struct cpumask *)cpumask_of(0);
> diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
> index 03e7c2d49559..94640c3491d7 100644
> --- a/arch/x86/include/asm/special_insns.h
> +++ b/arch/x86/include/asm/special_insns.h
> @@ -117,7 +117,20 @@ static inline void wrpkru(u32 pkru)
>  
>  static __always_inline void wbinvd(void)
>  {
> -	asm volatile("wbinvd": : :"memory");
> +	asm volatile("wbinvd" : : : "memory");
> +}
> +
> +/*
> + * Cheaper version of wbinvd(). Call when caches
> + * need to be written back but not invalidated.
> + */
> +static __always_inline void wbnoinvd(void)
> +{
> +	/*
> +	 * Use the compatible but more destructive "invalidate"
> +	 * variant when no-invalidate is unavailable.
> +	 */
> +	alternative("wbinvd", "wbnoinvd", X86_FEATURE_WBNOINVD);

The minimal version of binutils kernel supports is 2.25 which doesn't
know about WBNOINVD.

I think you need to do something like.

	alternative("wbinvd", ".byte 0xf3; wbinvd", X86_FEATURE_WBNOINVD);

Or propose to bump minimal binutils version.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov