[RFC,v3,4/4] Documentation/admin-guide: Change doc for split_lock_detect parameter
diff mbox series

Message ID 20201031002714.3649728-5-fenghua.yu@intel.com
State New, archived
Headers show
Series
  • x86/bus_lock: Enable bus lock detection
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Commit Message

Fenghua Yu Oct. 31, 2020, 12:27 a.m. UTC
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@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
Change Log:
- Simplify the documentation (Randy).

 .../admin-guide/kernel-parameters.txt         | 28 +++++++++++++++----
 1 file changed, 23 insertions(+), 5 deletions(-)

Comments

Randy Dunlap Oct. 31, 2020, 3:14 a.m. UTC | #1
Hi,

On 10/30/20 5:27 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@intel.com>
> Reviewed-by: Tony Luck <tony.luck@intel.com>
> ---
> Change Log:
> - Simplify the documentation (Randy).
> 
>  .../admin-guide/kernel-parameters.txt         | 28 +++++++++++++++----
>  1 file changed, 23 insertions(+), 5 deletions(-)
> 
> 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.

> +
> +				  N/A for split lock detection.
>  
>  			If an #AC exception is hit in the kernel or in
>  			firmware (i.e. not while executing in user mode)
>  			the kernel will oops in either "warn" or "fatal"
>  			mode.
>  
> +			#DB exception for bus lock is triggered only when
> +			CPL > 0.
> +

thanks.
Fenghua Yu Nov. 2, 2020, 5:03 p.m. UTC | #2
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

Patch
diff mbox series

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
 				  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
+				  detection or bus lock detection. Default
+				  behavior is from #DB if both features are
+				  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
+				  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
+				  user.
+
+				  N/A for split lock detection.
 
 			If an #AC exception is hit in the kernel or in
 			firmware (i.e. not while executing in user mode)
 			the kernel will oops in either "warn" or "fatal"
 			mode.
 
+			#DB exception for bus lock is triggered only when
+			CPL > 0.
+
 	srbds=		[X86,INTEL]
 			Control the Special Register Buffer Data Sampling
 			(SRBDS) mitigation.