linux-kernel - Re: [PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE

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Message-ID: <20191025142248.GD6483@zn.tnic>
Date:   Fri, 25 Oct 2019 16:22:48 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Tony Luck <tony.luck@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 02/16] x86/mce: WARN once if IA32_FEATURE_CONTROL MSR
 is left unlocked

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@...hat.com>
> Cc: Wanpeng Li <wanpengli@...cent.com>
> Cc: Jim Mattson <jmattson@...gle.com>
> Cc: kvm@...r.kernel.org
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  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@...e.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette