Messages in this thread | | | Date | Fri, 29 May 2015 19:44:39 +0200 | From | Borislav Petkov <> | Subject | Re: [Patch V1 2/3] x86, mce: Add infrastructure required to support LMCE |
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On Fri, May 29, 2015 at 09:28:01AM -0700, Ashok Raj wrote: > Initialization and handling for LMCE > - boot time option to disable LMCE for that boot instance > - Check for capability via IA32_MCG_CAP > - provide ability to enable/disable LMCE on demand. > > See http://www.intel.com/sdm Volume 3 System Programming Guide, Chapter 15 > for more information on MSR's and documentation on Local MCE. > > Signed-off-by: Ashok Raj <ashok.raj@intel.com> > --- > Documentation/x86/x86_64/boot-options.txt | 3 ++ > arch/x86/include/asm/mce.h | 5 +++ > arch/x86/kernel/cpu/mcheck/mce.c | 3 ++ > arch/x86/kernel/cpu/mcheck/mce_intel.c | 75 +++++++++++++++++++++++++++++++ > 4 files changed, 86 insertions(+)
...
> +static bool lmce_supported(void) > +{ > + u64 cap, feature_ctl; > + bool lmce_bios_support, retval; > + > + if (mca_cfg.lmce_disabled) > + return false; > + > + rdmsrl(MSR_IA32_MCG_CAP, cap); > + rdmsrl(MSR_IA32_FEATURE_CONTROL, feature_ctl);
One more thing: You should check MCG_LMCE_P *first* and only read MSR_IA32_FEATURE_CONTROL if MCG_LMCE_P is set - otherwise this'll start blowing up on older machines which don't sport that new MSR and on kvm.
> + /* > + * BIOS should indicate support for LMCE by setting > + * bit20 in IA32_FEATURE_CONTROL. without which touching > + * MCG_EXT_CTL will generate #GP fault. > + */ > + lmce_bios_support = ((feature_ctl & (FEATURE_CONTROL_LMCE_BITS)) == > + (FEATURE_CONTROL_LMCE_BITS)); > + > + /* > + * MCG_CAP should indicate both MCG_SER_P and MCG_LMCE_P > + */
Also, why do we need to look at MCG_SER_P for LMCE?
Btw, we do that already in __mcheck_cpu_cap_init() so you could check mca_cfg.ser here instead.
> + cap = ((cap & MCG_CAP_LMCE_BITS) == (MCG_CAP_LMCE_BITS)); > + retval = (cap && lmce_bios_support);
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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