Re: [PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR is left unlocked

[Borislav Petkov]

On Mon, Oct 21, 2019 at 04:56:42PM -0700, Sean Christopherson wrote:
> WARN if the IA32_FEATURE_CONTROL MSR is somehow left unlocked now that
> CPU initialization unconditionally locks the MSR.
> 
> Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
> Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/mce/intel.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/intel.c b/arch/x86/kernel/cpu/mce/intel.c
> index 88cd9598fa57..1008f14b803b 100644
> --- a/arch/x86/kernel/cpu/mce/intel.c
> +++ b/arch/x86/kernel/cpu/mce/intel.c
> @@ -117,11 +117,10 @@ static bool lmce_supported(void)
>  	 * generate a #GP fault.
>  	 */
>  	rdmsrl(MSR_IA32_FEATURE_CONTROL, tmp);
> -	if ((tmp & (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE)) ==
> -		   (FEATURE_CONTROL_LOCKED | FEATURE_CONTROL_LMCE))
> -		return true;
> +	if (WARN_ON_ONCE(!(tmp & FEATURE_CONTROL_LOCKED)))
> +		return false;
>  
> -	return false;
> +	return tmp & FEATURE_CONTROL_LMCE;
>  }
>  
>  bool mce_intel_cmci_poll(void)
> -- 

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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