Include asm/processor.h to prevents compilation failures due to implicit
declaration of cpu_relax() in ex_handler_msr_mce() when compiling with
CONFIG_X86_MCE disabled.

Signed-off-by: Dmytro Maluka <dmaluka@chromium.org>
---
 arch/x86/include/asm/extable.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
index a0e0c6b50155..c22e524276a5 100644
--- a/arch/x86/include/asm/extable.h
+++ b/arch/x86/include/asm/extable.h
@@ -3,6 +3,7 @@
 #define _ASM_X86_EXTABLE_H
 
 #include <asm/extable_fixup_types.h>
+#include <asm/processor.h>	/* for cpu_relax() */
 
 /*
  * The exception table consists of two addresses relative to the
-- 
2.49.0.805.g082f7c87e0-goog

On Fri, Apr 18, 2025 at 11:57:00AM +0000, Dmytro Maluka wrote:
> Include asm/processor.h to prevents compilation failures due to implicit
> declaration of cpu_relax() in ex_handler_msr_mce() when compiling with
> CONFIG_X86_MCE disabled.

Builds fine here:

$ grep X86_MCE .config
# CONFIG_X86_MCE is not set

$ make -j...
...

  OBJCOPY arch/x86/boot/setup.bin
  BUILD   arch/x86/boot/bzImage
Kernel: arch/x86/boot/bzImage is ready  (#1)
$

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Fri, Apr 18, 2025 at 02:12:03PM +0200, Borislav Petkov wrote:
> On Fri, Apr 18, 2025 at 11:57:00AM +0000, Dmytro Maluka wrote:
> > Include asm/processor.h to prevents compilation failures due to implicit
> > declaration of cpu_relax() in ex_handler_msr_mce() when compiling with
> > CONFIG_X86_MCE disabled.
> 
> Builds fine here:
> 
> $ grep X86_MCE .config
> # CONFIG_X86_MCE is not set
> 
> $ make -j...
> ...
> 
>   OBJCOPY arch/x86/boot/setup.bin
>   BUILD   arch/x86/boot/bzImage
> Kernel: arch/x86/boot/bzImage is ready  (#1)
> $

Yeah, I meant precisely: when compiling with CONFIG_X86_MCE disabled and
some code enabled that includes asm/extable.h without prior including
asm/processor.h.

I encountered that with the out-of-tree-yet code [1] (which is a part of
a prototype implementation of pKVM on x86) which includes asm/sections.h
which includes asm/extable.h.

[1] https://github.com/intel-staging/pKVM-IA/blob/pvVMCS-POC-v6.12/arch/x86/kvm/pkvm/smp.c

On Fri, Apr 18, 2025 at 02:36:02PM +0200, Dmytro Maluka wrote:
> Yeah, I meant precisely: when compiling with CONFIG_X86_MCE disabled and
> some code enabled that includes asm/extable.h without prior including
> asm/processor.h.
> 
> I encountered that with the out-of-tree-yet code [1] (which is a part of
> a prototype implementation of pKVM on x86) which includes asm/sections.h
> which includes asm/extable.h.

Sorry, come back with this when you can trigger this solely with the upstream
kernel.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette