linux-kernel - Re: [PATCH v4] cper, apei, mce: Pass x86 CPER through the MCA handling chain

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Date:   Thu, 24 Sep 2020 12:23:27 -0500
From:   Smita Koralahalli Channabasappa <skoralah@....com>
To:     Punit Agrawal <punit1.agrawal@...hiba.co.jp>,
        Borislav Petkov <bp@...en8.de>
Cc:     Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
        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 v4] cper, apei, mce: Pass x86 CPER through the MCA
 handling chain

On 9/23/20 7:02 PM, Punit Agrawal wrote:

> Borislav Petkov <bp@...en8.de> writes:
>
>> Smita,
>>
>> pls sync the time of the box where you create the patch:
>>
>>   Date: Fri,  4 Sep 2020 09:04:44 -0500
>>
>> but your mail headers have:
>>
>>   Received: from ... with mapi id 15.20.3370.019; Fri, 18 Sep 2020 14:49:12 +0000
>>   						^^^^^^^^^^^^^^^^^^

Sorry for the trouble. I have fixed this.

>>> I know Boris asked you to add the reason for the Reported-by, but
>>> usually we don't track version differences in the committed patch.
>>>
>>> Boris, can you confirm if you want the Reported-by to be retained?
>> How else would you explain what the Reported-by: tag is for on a patch
>> which adds a feature?
> As Ard clarified, I was questioning the inclusion of the Reported-by:
> tag in the patch itself. But I also don't have enough of a strong
> opinion to obsess about it.
>
> [ Aside: One interesting consequence of this though is that by the same
> argument, changes resulting from comments on earlier versions are also
> legitimate content for the final patch. Not saying I agree. ]
>
>>>> + * The first expected register in the register layout of MCAX address space.
>>>> + * The address defined must match with the first MSR address extracted from
>>>> + * BERT which in SMCA systems is the bank's MCA_STATUS register.
>>>> + *
>>>> + * Note that the decoding of the raw MSR values in BERT is implementation
>>>> + * specific and follows register offset order of MCAX address space.
>>>> + */
>>>> +#define MASK_MCA_STATUS 0xC0002001
>>> The macro value is already defined in mce.h as
>>> MSR_AMD64_SMCA_MC0_STATUS.  Is there any reason to not use it?
>> Good point.

I indeed missed it. thanks!

>>> You can move the comment to where you check the status register.
>> No need if he really wants to use the first MCi_STATUS address.

Okay!

>>>> +	m.apicid = lapic_id;
>>>> +	m.bank = (ctx_info->msr_addr >> 4) & 0xFF;
>>>> +	m.status = *i_mce;
>>>> +	m.addr = *(i_mce + 1);
>>>> +	m.misc = *(i_mce + 2);
>>>> +	/* Skipping MCA_CONFIG */
>>>> +	m.ipid = *(i_mce + 4);
>>>> +	m.synd = *(i_mce + 5);
>>> Instead of using the raw pointer arithmetic, it is better to define a
>>> structure for the MCA registers? Something like -
>>>
>>>      struct {
>>>          u64 addr;
>>>          u64 misc;
>>>          u64 config;
>>>          u64 ipid;
>>>          ...
>>>      }
>>>
>>> Checking back, this was mentioned in the previous review comments as
>>> well. Please address all comments before posting a new version - either
>>> by following the suggestion or explaining why it is not a good idea.
>> Well, that was addressed in his reply last time:
>>
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.kernel.org%2Fr%2Fa28aa613-8353-0052-31f6-34bc733abf59%40amd.com&amp;data=02%7C01%7CSmita.KoralahalliChannabasappa%40amd.com%7C1e8d8042158141af2c0a08d8601d31d7%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637365025808391248&amp;sdata=C71Gp1ZNQhtckegVJbYPA%2FTNi6np%2Fl1Xl4BvI4kGX4Y%3D&amp;reserved=0
> Oops. My bad - sorry I missed the response.
>
> Copying the relevant comment here for discussion -
>
>>>> The registers here are implementation specific and applies only for
>>>> SMCA systems. So I have used pointer arithmetic as it is not defined
>>>> in the spec.
> Even though it's not defined in the UEFI spec, it doesn't mean a
> structure definition cannot be created. After all, the patch is relying
> on some guarantee of the meaning of the values and their ordering.
>
> If the patch is relying on the definitions in the SMCA spec it is a good
> idea to reference it here - both for review and providing relevant
> context for future developers.

Okay, I agree the structure definition will make the code less arbitrary
and provides relevant context compared to pointer arithmetic. I did not
think this way. I can try this out if no objections.

>> You might've missed it because you weren't CCed directly.
> Indeed, I missed it. Thanks for the pointer.

Sorry, I missed including you on CC. Will include henceforth!

Thanks,
Smita