linux-kernel - Re: [PATCH RFC v3 4/4] Documentation/admin-guide: Change doc for split_lock

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Date:   Mon, 2 Nov 2020 17:03:18 +0000
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Christopherson Sean J <sean.j.christopherson@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH RFC v3 4/4] Documentation/admin-guide: Change doc for
 split_lock_detect parameter

Hi, Randy,

On Fri, Oct 30, 2020 at 08:14:15PM -0700, Randy Dunlap wrote:
> On 10/30/20 5:27 PM, Fenghua Yu wrote:
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 526d65d8573a..ee419ce659f5 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -5044,27 +5044,45 @@
> >  	spia_peddr=
> >  
> >  	split_lock_detect=
> > -			[X86] Enable split lock detection
> > +			[X86] Enable split lock detection or bus lock detection
> >  
> >  			When enabled (and if hardware support is present), atomic
> >  			instructions that access data across cache line
> > -			boundaries will result in an alignment check exception.
> > +			boundaries will result in an alignment check exception
> > +			for split lock detection or a debug exception for
> > +			bus lock detection.
> >  
> >  			off	- not enabled
> >  
> >  			warn	- the kernel will emit rate limited warnings
> 
> 				                       rate-limited
> 
> >  				  about applications triggering the #AC
> > -				  exception. This mode is the default on CPUs
> > -				  that supports split lock detection.
> > +				  exception or the #DB exception. This mode is
> > +				  the default on CPUs that supports split lock
> 
> 				                           support
> 
> > +				  detection or bus lock detection. Default
> > +				  behavior is from #DB if both features are
> 
> I would say			           is by #DB
> 
> > +				  enabled in hardware.
> >  
> >  			fatal	- the kernel will send SIGBUS to applications
> > -				  that trigger the #AC exception.
> > +				  that trigger the #AC exception or the #DB
> > +				  exception. Default behavior is from #AC
> 
> and				                              is by #AC
> 
> > +				  if both features are enabled in hardware.
> > +
> > +			ratelimit:N -
> > +				  Set rate limit to N bus locks per second
> > +				  for bus lock detection. 0 < N <= HZ/2 and
> > +				  N is approximate. Only applied to non root
> 
> 				                                    non-root
> 
> > +				  user.
> 
> 				  users.

I'll fix the issues in the next version.

Thank you very much for your review!

-Fenghua