linux-kernel - Re: [PATCH] x86/MCE/AMD: Clear DFR errors found in THR handler

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Date:   Thu, 27 Oct 2022 15:01:38 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        tony.luck@...el.com, x86@...nel.org,
        Smita.KoralahalliChannabasappa@....com
Subject: Re: [PATCH] x86/MCE/AMD: Clear DFR errors found in THR handler

On Thu, Oct 27, 2022 at 01:46:24PM +0200, Borislav Petkov wrote:
> On Tue, Jun 21, 2022 at 03:59:43PM +0000, Yazen Ghannam wrote:
> > AMD's MCA Thresholding feature counts errors of all severites not just
> > correctable errors. If a deferred error causes the threshold limit to be
> > reached (it was the error that caused the overflow), then both a
> > deferred error interrupt and a thresholding interrupt will be triggered.
> > 
> > The order of the interrupts is not guaranteed. If the threshold
> > interrupt handler is executed first, then it will clear MCA_STATUS for
> > the error. It will not check or clear MCA_DESTAT which also holds a copy
> > of the deferred error. When the deferred error interrupt handler runs it
> > will not find an error in MCA_STATUS, but it will find the error in
> > MCA_DESTAT. This will cause two errors to be logged.
> > 
> > Check for deferred errors when handling a threshold interrupt. If a bank
> > contains a deferred error, then clear the bank's MCA_DESTAT register.
> > 
> > Define a new helper function to do the deferred error check and clearing
> > of MCA_DESTAT.
> > 
> > Fixes: 37d43acfd79f ("x86/mce/AMD: Redo error logging from APIC LVT interrupt handlers")
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> > Cc: stable@...r.kernel.org
> > ---
> >  arch/x86/kernel/cpu/mce/amd.c | 37 +++++++++++++++++++++++------------
> >  1 file changed, 24 insertions(+), 13 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
> > index 1c87501e0fa3..ab1145cf8328 100644
> > --- a/arch/x86/kernel/cpu/mce/amd.c
> > +++ b/arch/x86/kernel/cpu/mce/amd.c
> > @@ -788,6 +788,28 @@ _log_error_bank(unsigned int bank, u32 msr_stat, u32 msr_addr, u64 misc)
> >  	return status & MCI_STATUS_DEFERRED;
> >  }
> >  
> > +static bool _log_error_deferred(unsigned int bank, u32 misc)
> > +{
> > +	bool defrd;
> > +
> > +	defrd = _log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
> > +				mca_msr_reg(bank, MCA_ADDR), misc);
> > +
> > +	if (!defrd)
> > +		return false;
> 
> I've zapped that defrd variable:
> 
> diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
> index ab1145cf8328..6ae7edea3270 100644
> --- a/arch/x86/kernel/cpu/mce/amd.c
> +++ b/arch/x86/kernel/cpu/mce/amd.c
> @@ -790,12 +790,8 @@ _log_error_bank(unsigned int bank, u32 msr_stat, u32 msr_addr, u64 misc)
>  
>  static bool _log_error_deferred(unsigned int bank, u32 misc)
>  {
> -	bool defrd;
> -
> -	defrd = _log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
> -				mca_msr_reg(bank, MCA_ADDR), misc);
> -
> -	if (!defrd)
> +	if (!_log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
> +			     mca_msr_reg(bank, MCA_ADDR), misc))
>  		return false;
>  
>  	/*
> 
> -- 

Yep, looks good to me. Thanks!

-Yazen