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Date:   Tue, 11 Apr 2023 14:32:34 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Tony Luck <tony.luck@intel.com>
Cc:     Yazen Ghannam <yazen.ghannam@amd.com>,
        Smita.KoralahalliChannabasappa@amd.com,
        dave.hansen@linux.intel.com, x86@kernel.org,
        linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
Subject: Re: [PATCH v4 2/5] x86/mce: Add per-bank CMCI storm mitigation
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References: <ZCRYl9c7xgIJ+pJe@yaz-sghr>
 <20230403210716.347773-1-tony.luck@intel.com>
 <20230403210716.347773-3-tony.luck@intel.com>
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On Mon, Apr 03, 2023 at 02:07:13PM -0700, Tony Luck wrote:
> Add a hook into machine_check_poll() to keep track of per-CPU, per-bank
> corrected error logs.
> 
> Maintain a bitmap history for each bank showing whether the bank
> logged an corrected error or not each time it is polled.
> 
> In normal operation the interval between polls of this banks
> determines how far to shift the history. The 64 bit width corresponds
> to about one second.
> 
> When a storm is observed the Rate of interrupts is reduced by setting
> a large threshold value for this bank in IA32_MCi_CTL2. This bank is
> added to the bitmap of banks for this CPU to poll. The polling rate
> is increased to once per second.
> During a storm each bit in the history indicates the status of the
> bank each time it is polled. Thus the history covers just over a minute.
> 
> Declare a storm for that bank if the number of corrected interrupts
> seen in that history is above some threshold (5 in this RFC code for
> ease of testing, likely move to 15 for compatibility with previous
> storm detection).
> 
> A storm on a bank ends if enough consecutive polls of the bank show
> no corrected errors (currently 30, may also change). That resets the
> threshold in IA32_MCi_CTL2 back to 1, removes the bank from the bitmap
> for polling, and changes the polling rate back to the default.
> 
> If a CPU with banks in storm mode is taken offline, the new CPU
> that inherits ownership of those banks takes over management of
> storm(s) in the inherited bank(s).
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
> Tested-by: Yazen Ghannam <yazen.ghannam@amd.com>
> ---
>  arch/x86/kernel/cpu/mce/internal.h |   4 +-
>  arch/x86/kernel/cpu/mce/core.c     |  26 ++++--
>  arch/x86/kernel/cpu/mce/intel.c    | 139 ++++++++++++++++++++++++++++-
>  3 files changed, 158 insertions(+), 11 deletions(-)

ld: vmlinux.o: in function `machine_check_poll':
/home/boris/kernel/2nd/linux/arch/x86/kernel/cpu/mce/core.c:683: undefined reference to `track_cmci_storm'
make[1]: *** [scripts/Makefile.vmlinux:35: vmlinux] Error 1
make: *** [Makefile:1249: vmlinux] Error 2
make: *** Waiting for unfinished jobs....

-- 
Regards/Gruss,
    Boris.

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