linux-kernel - Re: [PATCH 2/2] x86/MCE: Don't call kill_me

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Message-ID: <20210504180734.GA721714@agluck-desk2.amr.corp.intel.com>
Date:   Tue, 4 May 2021 11:07:34 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Yazen Ghannam <Yazen.Ghannam@....com>
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, Smita.KoralahalliChannabasappa@....com,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/MCE: Don't call kill_me_now() directly

On Tue, May 04, 2021 at 05:47:12PM +0000, Yazen Ghannam wrote:
> From: Yazen Ghannam <yazen.ghannam@....com>
> 
> Always call kill_me_maybe() in order to attempt memory recovery. This
> ensures that any memory associated with the error is properly marked as
> poison.
> 
> This is needed for errors that occur on memory, but that do not have
> MCG_STATUS[RIPV] set. One example is data poison consumption through the
> instruction fetch units on AMD Zen-based systems.
> 
> The MF_MUST_KILL flag is passed to memory_failure() when
> MCG_STATUS[RIPV] is not set. So the associated process will still be
> killed.
> 
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> ---
>  arch/x86/kernel/cpu/mce/core.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 308fb644b94a..9040d45ed997 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -1285,10 +1285,7 @@ static void queue_task_work(struct mce *m, int kill_current_task)
>  	current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV);
>  	current->mce_whole_page = whole_page(m);
>  
> -	if (kill_current_task)
> -		current->mce_kill_me.func = kill_me_now;
> -	else
> -		current->mce_kill_me.func = kill_me_maybe;
> +	current->mce_kill_me.func = kill_me_maybe;
>  
>  	task_work_add(current, &current->mce_kill_me, TWA_RESUME);
>  }

Could we just get rid of kill_me_now() at the same time? It's only
one line, and with this change only called in one place (from
kill_me_maybe()) ... just put the force_sig(SIGBUS); inline?

-Tony