linux-kernel - Re: [PATCH 03/31] x86: MCE: Fix EIPV behaviour with !PCC

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Date:	Wed, 27 May 2009 13:30:24 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	linux-kernel@...r.kernel.org, hpa@...or.com, x86@...nel.org,
	Huang Ying <ying.huang@...el.com>,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 03/31] x86: MCE: Fix EIPV behaviour with !PCC

Andi Kleen wrote:
> From: Huang Ying <ying.huang@...el.com>
> 
> Impact: Spec compliance
> 
> When tolerant == 0, system should go panic instead of send SIGBUS even
> for a MCE with EPIV && !PCC on user space.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 3f158d7..e1271ac 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -485,7 +485,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
>  		 * force_sig() takes an awful lot of locks and has a slight
>  		 * risk of deadlocking.
>  		 */
> -		if (user_space) {
> +		if (user_space && tolerant > 0) {
>  			force_sig(SIGBUS, current);
>  		} else if (panic_on_oops || tolerant < 2) {
>  			mce_panic("Uncorrected machine check",

Again, this patch is useless.

                if (m.status & MCI_STATUS_EN) {
                        /* if PCC was set, there's no way out */
                        no_way_out |= !!(m.status & MCI_STATUS_PCC);
                        /*
                         * If this error was uncorrectable and there was
                         * an overflow, we're in trouble.  If no overflow,
                         * we might get away with just killing a task.
                         */
                        if (m.status & MCI_STATUS_UC) {
                                if (tolerant < 1 || m.status & MCI_STATUS_OVER)
                                        no_way_out = 1;
                                kill_it = 1;
                        }
                } else {
 :
        if (no_way_out && tolerant < 3)
                mce_panic("Machine check", &panicm, mcestart);
 :
        if (kill_it && tolerant < 3) {
 :
                if (user_space) {
                        force_sig(SIGBUS, current);
                } else if (panic_on_oops || tolerant < 2) {
                        mce_panic("Uncorrected machine check",
                                &panicm, mcestart);
                }
        }

We never reach there with tolerant == 0.

And you will remove this code in your 25/31.


Thanks,
H.Seto

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