linux-kernel - Re: [PATCH v3 2/2] x86/mce/dev-mcelog: Fix updating kflags in AMD systems

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Date:   Mon, 14 Sep 2020 16:20:53 -0500
From:   Smita Koralahalli Channabasappa <skoralah@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-edac@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-acpi@...r.kernel.org,
        devel@...ica.org, Tony Luck <tony.luck@...el.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH v3 2/2] x86/mce/dev-mcelog: Fix updating kflags in AMD
 systems

On 9/14/20 10:34 AM, Borislav Petkov wrote:

> On Thu, Sep 03, 2020 at 06:45:31PM -0500, Smita Koralahalli wrote:
>> The mcelog utility is not commonly used on AMD systems. Therefore, errors
>> logged only by the dev_mce_log() notifier will be missed. This may occur
>> if the EDAC modules are not loaded in which case it's preferable to print
>> the error record by the default notifier.
>>
>> However, the mce->kflags set by dev_mce_log() notifier makes the default
>> notifier to skip over the errors assuming they are processed by
>> dev_mce_log().
>>
>> Do not update kflags in the dev_mce_log() notifier on AMD systems.
>>
>> Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
>> ---
>> Link:
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.kernel.org%2Fr%2F20200828203332.11129-3-Smita.KoralahalliChannabasappa%40amd.com&amp;data=02%7C01%7CSmita.KoralahalliChannabasappa%40amd.com%7Cc452e9f80fe9459839c708d858c3a763%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637356944652485754&amp;sdata=%2FhYQbBBNld1GtNX8%2FI6PERD0icYfy0e1k5zukQYI%2Fa4%3D&amp;reserved=0
>>
>> v3:
>> 	No change
>> v2:
>> 	No change
>> ---
>>   arch/x86/kernel/cpu/mce/dev-mcelog.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mce/dev-mcelog.c b/arch/x86/kernel/cpu/mce/dev-mcelog.c
>> index 03e51053592a..100fbeebdc72 100644
>> --- a/arch/x86/kernel/cpu/mce/dev-mcelog.c
>> +++ b/arch/x86/kernel/cpu/mce/dev-mcelog.c
>> @@ -67,7 +67,9 @@ static int dev_mce_log(struct notifier_block *nb, unsigned long val,
>>   unlock:
>>   	mutex_unlock(&mce_chrdev_read_mutex);
>>   
>> -	mce->kflags |= MCE_HANDLED_MCELOG;
>> +	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
>> +		mce->kflags |= MCE_HANDLED_MCELOG;
>> +
>>   	return NOTIFY_OK;
>>   }
>>   
>> -- 
> This one is not related to your 1/2 so it sounds to me like I should
> take this one now, independently?

Yes, this can be taken independently. I just tagged it along as I came
across the issue of missing error logs while trying to print error
records in the previous patch.

Thanks,
Smita