linux-kernel - Re: [PATCH 2/3] x86, ras: Extend machine check recovery code to annotated ring0 areas

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Date:	Tue, 10 Nov 2015 14:11:35 -0800
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH 2/3] x86, ras: Extend machine check recovery code to
 annotated ring0 areas

On Tue, Nov 10, 2015 at 12:21:42PM +0100, Borislav Petkov wrote:
> You could save a precious indentation level here:
> 
> 	if (cfg->tolerant == 3)
> 		goto clear;
> 
> and add the "clear" label below.
> 
> clear:
>         if (worst > 0)
>                 mce_report_event(regs);
>         mce_wrmsrl(MSR_IA32_MCG_STATUS, 0)
> 
> >  		if (no_way_out)
> >  			mce_panic("Fatal machine check on current CPU", &m, msg);
> >  		if (worst == MCE_AR_SEVERITY) {
> > -			recover_paddr = m.addr;
> > -			if (!(m.mcgstatus & MCG_STATUS_RIPV))
> > -				flags |= MF_MUST_KILL;
> > +			if ((m.cs & 3) == 3) {
> > +				recover_paddr = m.addr;
> > +				if (!(m.mcgstatus & MCG_STATUS_RIPV))
> > +					flags |= MF_MUST_KILL;
> > +			} else if (fixup_mcexception(regs)) {
> > +				regs->ax = BIT(63) | m.addr;
> > +			} else
> > +				mce_panic("Failed kernel mode recovery",
> > +					  &m, NULL);
> >  		} else if (kill_it) {
> >  			force_sig(SIGBUS, current);
> >  		}

That would be tidier ... the inside of the "if" has been gradually growing
with added recovery paths.  I had to fold the mce_panic() line to shut
checkpatch up.

But I'm not really sure what tolerant==3 people really want here. By skipping
the recovery code they doom themselves to hitting the machine check again.

-Tony
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