On 2024-03-27 4:25 PM, Andrew Morton wrote:

On Wed, 27 Mar 2024 13:00:43 -0700 Samuel Holland [off-list ref] wrote:

quoted

Now that all previously-supported architectures select
ARCH_HAS_KERNEL_FPU_SUPPORT, this code can depend on that symbol instead
of the existing list of architectures. It can also take advantage of the
common kernel-mode FPU API and method of adjusting CFLAGS.

...

@@ -87,16 +78,9 @@ void dc_fpu_begin(const char *function_name, const int line)
 	WARN_ON_ONCE(!in_task());
 	preempt_disable();
 	depth = __this_cpu_inc_return(fpu_recursion_depth);
-
 	if (depth == 1) {
-#if defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
+		BUG_ON(!kernel_fpu_available());
 		kernel_fpu_begin();

For some reason kernel_fpu_available() was undefined in my x86_64
allmodconfig build.  I just removed the statement.

This is because the include guard in asm/fpu.h conflicts with the existing one
in asm/fpu/types.h (which doesn't match its filename), so the definition of
kernel_fpu_available() is not seen. I can fix up the include guard in
asm/fpu/types.h in the next version:

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index ace9aa3b78a3..75a3910d867a 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h

@@ -2,8 +2,8 @@
 /*
  * FPU data structures:
  */
-#ifndef _ASM_X86_FPU_H
-#define _ASM_X86_FPU_H
+#ifndef _ASM_X86_FPU_TYPES_H
+#define _ASM_X86_FPU_TYPES_H

 #include <asm/page_types.h>

@@ -596,4 +596,4 @@ struct fpu_state_config {
 /* FPU state configuration information */
 extern struct fpu_state_config fpu_kernel_cfg, fpu_user_cfg;

-#endif /* _ASM_X86_FPU_H */
+#endif /* _ASM_X86_FPU_TY{ES_H */

Regards,
Samuel