Re: [PATCH] x86: mce: Honour bios-set CMCI threshold

[Naveen N. Rao]

On 08/22/2012 06:16 PM, Borislav Petkov wrote:
> On Wed, Aug 22, 2012 at 06:00:54PM +0530, Naveen N. Rao wrote:
> > The ACPI spec doesn't provide for a way for the bios to pass down
> > recommended thresholds to the OS on a _per-bank_ basis. This patch adds
> > a new boot option, which if passed, allows bios to initialize the CMCI
> > threshold. In such a case, we simply skip programming any threshold
> > value.
> >
> > As fail-safe, we initialize threshold to 1 if some banks have not been
> > initialized by the bios and warn the user.
> >
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> > ---
> >   Documentation/x86/x86_64/boot-options.txt |    5 ++++
> >   arch/x86/include/asm/mce.h                |    1 +
> >   arch/x86/kernel/cpu/mcheck/mce.c          |    4 +++
> >   arch/x86/kernel/cpu/mcheck/mce_intel.c    |   39 +++++++++++++++++++++++++++--
> >   4 files changed, 46 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
> > index c54b4f5..ec92540 100644
> > --- a/Documentation/x86/x86_64/boot-options.txt
> > +++ b/Documentation/x86/x86_64/boot-options.txt
> > @@ -50,6 +50,11 @@ Machine check
> >   		monarchtimeout:
> >   		Sets the time in us to wait for other CPUs on machine checks. 0
> >   		to disable.
> > +   mce=bios_cmci_threshold
> > +		Don't overwrite the bios-set CMCI threshold. This boot option
> > +		prevents Linux from overwriting the CMCI threshold set by the
> > +		bios. Without this option, Linux always sets the CMCI
> > +		threshold to 1.
> >
> >      nomce (for compatibility with i386): same as mce=off
> >
> > diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
> > index a3ac52b..8ad5078 100644
> > --- a/arch/x86/include/asm/mce.h
> > +++ b/arch/x86/include/asm/mce.h
> > @@ -171,6 +171,7 @@ DECLARE_PER_CPU(struct device *, mce_device);
> >   #ifdef CONFIG_X86_MCE_INTEL
> >   extern int mce_cmci_disabled;
> >   extern int mce_ignore_ce;
> > +extern int mce_bios_cmci_threshold;
> >   void mce_intel_feature_init(struct cpuinfo_x86 *c);
> >   void cmci_clear(void);
> >   void cmci_reenable(void);
> > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> > index 292d025..401359d 100644
> > --- a/arch/x86/kernel/cpu/mcheck/mce.c
> > +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> > @@ -82,6 +82,7 @@ static int			mce_panic_timeout	__read_mostly;
> >   static int			mce_dont_log_ce		__read_mostly;
> >   int				mce_cmci_disabled	__read_mostly;
> >   int				mce_ignore_ce		__read_mostly;
> > +int				mce_bios_cmci_threshold	__read_mostly;
> >   int				mce_ser			__read_mostly;
>
> AFAICT, this is actually a single-bit flag but we're using a whole
> integer for it and from looking at the other boot options a couple of
> them are used as flags too.
>
> Care to define a
>
> struct boot_flags {
> 	__u64 	mce_bios_cmci_threshold : 1,
> 		__reserved		: 63;
> };
>
> and use
>
> 	boot_flags.mce_bios_cmci_threshold
>
> in the conditionals below instead?

Sure - that sounds like a good idea. Further, a #define can be used to 
avoid the need to change other references, though I'm not sure it's 
considered good practice:

#define mce_bios_cmci_threshold   boot_flags.mce_bios_cmci_threshold


Thanks!
- Naveen

> I'll try to convert the rest of them to that struct and thus save some
> more space...
>
> Thanks.

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