linux-kernel - Re: [PATCH v2 1/3] x86/mce/inject: Remove call to mce_notify

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Message-ID: <20250217114735.GAZ7Mh12l48HmAXXm7@fat_crate.local>
Date: Mon, 17 Feb 2025 12:47:35 +0100
From: Borislav Petkov <bp@...en8.de>
To: Nikolay Borisov <nik.borisov@...e.com>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, tony.luck@...el.com
Subject: Re: [PATCH v2 1/3] x86/mce/inject: Remove call to mce_notify_irq()

On Mon, Feb 17, 2025 at 01:20:55PM +0200, Nikolay Borisov wrote:
> Actually there is no loss of functionality since after an MCE is injected
> the early notifier will correctly call the usermode helper. So I
> think the following change log better reflects the situation:
> 
> 
>     x86/mce/inject: Remove call to mce_notify_irq()
>     The call to mce_notify_irq() has been there since the initial version of
>     the soft inject mce machinery, introduced in ea149b36c7f5 ("x86,
>     mce: add basic error injection infrastructure"). At that time it was
>     functional since injecting an MCE resulted in the following call chain:
>     raise_mce()
>       ->machine_check_poll()
>           ->mce_log() - sets notfiy_user_bit
>     ->mce_notify_user() (current mce_notify_irq) consumed the bit and called the
>     usermode helper.
>     However, with the introduction of 011d82611172 ("RAS: Add a Corrected Errors Collector")
>     the code got moved around and the user mode helper began to be called
>     via the early notifier (mce_first_notifier()) rendering the remaining call
>     in raise_local() defunct as the mce_need_notify bit (ex notify_user) is
>     only being set from the early notifier.
>     Remove the noop call and make mce_notify_irq static. No functional
>     changes.

Ah, there was that. We're doing a serious dance just to log an error, that's
for sure.

Yeah, that makes sense.

Thx.

-- 
Regards/Gruss,
    Boris.

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