Re: [PATCH v3 3/3] x86/mce: Add CMCI storm switching support for Zhaoxin

[Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>]

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On 2024/9/20 20:09, Tony W Wang-oc wrote:
> 
> 
> On 2024/9/20 19:44, Zhuo, Qiuxu wrote:
>>
>>
>>> From: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
>>> [...]
>>>>> --- a/arch/x86/kernel/cpu/mce/zhaoxin.c
>>>>> +++ b/arch/x86/kernel/cpu/mce/zhaoxin.c
>>>>> @@ -63,3 +63,21 @@ void mce_zhaoxin_feature_clear(struct cpuinfo_x86
>>>>> *c) {
>>>>>         intel_clear_lmce();
>>>>>    }
>>>>> +
>>>>> +void mce_zhaoxin_handle_storm(int bank, bool on) {
>>>>> +     unsigned long flags;
>>>>> +     u64 val;
>>>>> +
>>>>> +     raw_spin_lock_irqsave(&cmci_discover_lock, flags);
>>>>> +     rdmsrl(MSR_IA32_MCx_CTL2(bank), val);
>>>>> +     if (on) {
>>>>> +             val &= ~(MCI_CTL2_CMCI_EN |
>>>>> MCI_CTL2_CMCI_THRESHOLD_MASK);
>>>>> +             val |= CMCI_STORM_THRESHOLD;
>>>>> +     } else {
>>>>> +             val &= ~MCI_CTL2_CMCI_THRESHOLD_MASK;
>>>>> +             val |= (MCI_CTL2_CMCI_EN | cmci_threshold[bank]);
>>>>> +     }
>>>>> +     wrmsrl(MSR_IA32_MCx_CTL2(bank), val);
>>>>> +     raw_spin_unlock_irqrestore(&cmci_discover_lock, flags); }
>>>>
>>>> Are there any reasons or comments why it needs to disable/enable the
>>>> CMCI interrupt here during a CMCI storm on/off? If not, then reuse
>>>> mce_intel_handle_storm() to avoid duplicating the code.
>>>>
>>>
>>> As explained in another email.
>>> The reason is actually mentioned in the cover letter: "because 
>>> Zhaoxin's UCR
>>> error is not reported through CMCI", and we want to disable CMCI 
>>> interrupt
>>> when CMCI storm happened.
>>
>> So, this is just you want to disable CMCI when a CMCI storm happens.
>> This doesn't explain much to me.
>> What's the problem if not disable CMCI when a CMCI storm happens?
>>
> 
> In practice, we have encountered a lot of CE errors such as DRAM CE 
> errors, so it feels safer to disable CMCI interrupt than to set a large 
> threshold. At the same time, Zhaoxin's UCR is not reported through CMCI, 
> so we implemented like this.
> 
> Sincerely
> TonyWWang-oc
>