linux-kernel - Re: [PATCH 5/5] x86/mce/mce-inject: Return error code to userspace from mce-inject module

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Date:   Fri, 24 Sep 2021 10:26:55 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>, yazen.ghannam@....com
Subject: Re: [PATCH 5/5] x86/mce/mce-inject: Return error code to userspace
 from mce-inject module

On Wed, Sep 15, 2021 at 06:27:39PM -0500, Smita Koralahalli wrote:
> Currently, the mce-inject module fails silently and user must look for
> kernel logs to determine if the injection has succeeded.
> 
> Save time for the user and return error code from the module if error
> injection fails.
> 
> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> ---
>  arch/x86/kernel/cpu/mce/inject.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
> index c7d1564f244b..0ef9ff921c6a 100644
> --- a/arch/x86/kernel/cpu/mce/inject.c
> +++ b/arch/x86/kernel/cpu/mce/inject.c
> @@ -549,8 +549,10 @@ static void do_inject(void)
>  	}
>  
>  	cpus_read_lock();
> -	if (!cpu_online(cpu))
> +	if (!cpu_online(cpu)) {
> +		mce_err.err = -ENODEV;

You could issue a pr_err() here too. That ENODEV probably turns into
"write failed" but that doesn't say why.

-- 
Regards/Gruss,
    Boris.

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