linux-kernel - Re: [PATCH RFC v2 4/4] Documentation: Change doc for split_lock

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Message-ID: <20201030194222.GB3568909@otcwcpicx6.sc.intel.com>
Date:   Fri, 30 Oct 2020 19:42:22 +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 v2 4/4] Documentation: Change doc for
 split_lock_detect parameter

Hi, Randy,

On Wed, Oct 28, 2020 at 10:14:20PM -0700, Randy Dunlap wrote:
> On 10/28/20 1:28 PM, Fenghua Yu wrote:
> > Since #DB for bus lock detect changes the split_lock_detect parameter,
> > update the documentation for the changes.
> > 
> > Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> > Reviewed-by: Tony Luck <tony.luck@...el.com>
> > ---
> >  .../admin-guide/kernel-parameters.txt         | 47 +++++++++++++++----
> >  1 file changed, 39 insertions(+), 8 deletions(-)
> > 
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 526d65d8573a..51312484c2b6 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -5044,27 +5044,58 @@
> >  	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 an debug exception for
> > +			bus lock detection.
> >  
> >  			off	- not enabled
> >  
> > -			warn	- the kernel will emit rate limited warnings
> > -				  about applications triggering the #AC
> > -				  exception. This mode is the default on CPUs
> > -				  that supports split lock detection.
> > +			warn	- Default mode.
> >  
> > -			fatal	- the kernel will send SIGBUS to applications
> > -				  that trigger the #AC exception.
> > +				  If split lock detection is enabled in
> > +				  hardware, the kernel will emit rate limited
> > +				  warnings about applications triggering the #AC
> > +				  exception.
> > +
> > +				  If bus lock detection is enabled in hardware,
> > +				  the kernel will emit rate limited warnings
> > +				  about applications triggering the #DB
> > +				  exception.
> > +
> > +				  Default behavior is from bus lock detection
> > +				  if both features are enabled in hardware.
> > +
> > +			fatal	- If split lock detection is enabled in
> > +				  hardware, the kernel will send SIGBUS to
> > +				  applications that trigger the #AC exception.
> > +
> > +				  If bus lock detection is enabled in hardware,
> > +				  the kernel will send SIGBUS to application
> > +				  that trigger the #DB exception.
> > +
> > +				  Default behavior is from split lock detection
> > +				  if both are enabled in hardware.
> > +
> 
> Hi,
> This appears to have quite a bit of duplicated lines....

Ok. I will simplify this paragraph.

Thank you very much for your review!

-Fenghua