From ccb7735a1ea22621f21c3133e4f5f3da5fe5f5b7 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 27 Jan 2025 14:45:23 -0800 Subject: [PATCH] x86/fpu: Fully optimize out WARN_ON_FPU() Currently WARN_ON_FPU evaluates its argument even if CONFIG_X86_DEBUG_FPU is disabled, which adds unnecessary instructions to several functions, for example kernel_fpu_begin(). Fix this by using BUILD_BUG_ON_INVALID(x) in the no-debug case rather than (void)(x). Fixes: 83242c515881 ("x86/fpu: Make WARN_ON_FPU() more robust in the !CONFIG_X86_DEBUG_FPU case") Suggested-by: Sean Christopherson Signed-off-by: Eric Biggers Signed-off-by: Dave Hansen Link: https://lore.kernel.org/all/20250127224523.94300-1-ebiggers%40kernel.org --- arch/x86/kernel/fpu/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/internal.h b/arch/x86/kernel/fpu/internal.h index dbdb31f55fc7f..975de070c9c98 100644 --- a/arch/x86/kernel/fpu/internal.h +++ b/arch/x86/kernel/fpu/internal.h @@ -18,7 +18,7 @@ static __always_inline __pure bool use_fxsr(void) #ifdef CONFIG_X86_DEBUG_FPU # define WARN_ON_FPU(x) WARN_ON_ONCE(x) #else -# define WARN_ON_FPU(x) ({ (void)(x); 0; }) +# define WARN_ON_FPU(x) ({ BUILD_BUG_ON_INVALID(x); 0; }) #endif /* Used in init.c */