linux-kernel - Re: [PATCH v4 2/5] x86/mce: Add per-bank CMCI storm mitigation

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Message-ID: <6b6e53c5-8562-8ea0-befa-88c8b38663d6@amd.com>
Date:   Tue, 11 Apr 2023 10:06:45 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>, Tony Luck <tony.luck@...el.com>
Cc:     yazen.ghannam@....com, Smita.KoralahalliChannabasappa@....com,
        dave.hansen@...ux.intel.com, x86@...nel.org,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH v4 2/5] x86/mce: Add per-bank CMCI storm mitigation

On 4/11/23 08:32, Borislav Petkov wrote:
> 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@...el.com>
>> Reviewed-by: Yazen Ghannam <yazen.ghannam@....com>
>> Tested-by: Yazen Ghannam <yazen.ghannam@....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....
> 

Ah, this is with CONFIG_MCE_INTEL=n and everything =y. Is there an automated
way to test every config, not just random, combination in a subsystem?

I'll try to add something like this to my flow. It seems allnoconfig,
defconfig, etc. aren't enough. And it's too easy to overlook during code review.

Thanks,
Yazen