x86/mce: update outdated comment for refactored ex_has_fault_handler()

[PATCH] x86/mce: update outdated comment for refactored ex_has_fault_handler()

Posted by Kexin Sun 1 week, 6 days ago

The function ex_has_fault_handler() was refactored into
ex_get_fault_handler_type() by commit a05d54c41ecf ("x86/mce:
Provide method to find out the type of an exception handler"),
and then into ex_get_fixup_type() by commit 46d28947d987
("x86/extable: Rework the exception table mechanics").

The comment in do_machine_check() still referenced the old
function and _ASM_EXTABLE_FAULT().  Update the comment to
describe the current MCE-safe exception table mechanism
(EX_TYPE_FAULT_MCE_SAFE / EX_TYPE_DEFAULT_MCE_SAFE) and
the severity grading code that sets MCE_IN_KERNEL_RECOV.

Assisted-by: unnamed:deepseek-v3.2 coccinelle
Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
---
 arch/x86/kernel/cpu/mce/core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 8dd424ac5de8..fa9ab282cede 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1713,12 +1713,12 @@ noinstr void do_machine_check(struct pt_regs *regs)
 	} else {
 		/*
 		 * Handle an MCE which has happened in kernel space but from
-		 * which the kernel can recover: ex_has_fault_handler() has
-		 * already verified that the rIP at which the error happened is
-		 * a rIP from which the kernel can recover (by jumping to
-		 * recovery code specified in _ASM_EXTABLE_FAULT()) and the
-		 * corresponding exception handler which would do that is the
-		 * proper one.
+		 * which the kernel can recover: the severity grading code
+		 * has already verified that the rIP at which the error
+		 * happened is covered by an MCE-safe exception table entry
+		 * (EX_TYPE_FAULT_MCE_SAFE or EX_TYPE_DEFAULT_MCE_SAFE),
+		 * from which the kernel can recover by jumping to the
+		 * associated fixup code.
 		 */
 		if (m->kflags & MCE_IN_KERNEL_RECOV) {
 			if (!fixup_exception(regs, X86_TRAP_MC, 0, 0))
-- 
2.25.1

Re: [PATCH] x86/mce: update outdated comment for refactored ex_has_fault_handler()

Posted by Borislav Petkov 1 week, 6 days ago

On Sat, Mar 21, 2026 at 07:00:24PM +0800, Kexin Sun wrote:
> The function ex_has_fault_handler() was refactored into
> ex_get_fault_handler_type() by commit a05d54c41ecf ("x86/mce:
> Provide method to find out the type of an exception handler"),
> and then into ex_get_fixup_type() by commit 46d28947d987
> ("x86/extable: Rework the exception table mechanics").
> 
> The comment in do_machine_check() still referenced the old
> function and _ASM_EXTABLE_FAULT().  Update the comment to
> describe the current MCE-safe exception table mechanism
> (EX_TYPE_FAULT_MCE_SAFE / EX_TYPE_DEFAULT_MCE_SAFE) and
> the severity grading code that sets MCE_IN_KERNEL_RECOV.
> 
> Assisted-by: unnamed:deepseek-v3.2 coccinelle

You got assisted by an unnamed LLM agent to fix up a bunch of comments in the
kernel source?

> Signed-off-by: Kexin Sun <kexinsun@smail.nju.edu.cn>
> ---
>  arch/x86/kernel/cpu/mce/core.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 8dd424ac5de8..fa9ab282cede 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1713,12 +1713,12 @@ noinstr void do_machine_check(struct pt_regs *regs)
>  	} else {
>  		/*
>  		 * Handle an MCE which has happened in kernel space but from
> -		 * which the kernel can recover: ex_has_fault_handler() has
> -		 * already verified that the rIP at which the error happened is
> -		 * a rIP from which the kernel can recover (by jumping to
> -		 * recovery code specified in _ASM_EXTABLE_FAULT()) and the
> -		 * corresponding exception handler which would do that is the
> -		 * proper one.
> +		 * which the kernel can recover: the severity grading code
> +		 * has already verified that the rIP at which the error
> +		 * happened is covered by an MCE-safe exception table entry
> +		 * (EX_TYPE_FAULT_MCE_SAFE or EX_TYPE_DEFAULT_MCE_SAFE),
> +		 * from which the kernel can recover by jumping to the
> +		 * associated fixup code.

And when we change it again, there'll be more patches fixing up the comments?

I'd prefer if this comment is rewritten in a way that doesn't have to get
updated each time the code changes.

Thx.

-- 
Regards/Gruss,
    Boris.

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