linux-kernel - Re: [PATCH v6 3/7] acpi: apei: remove the unused code

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Date:   Thu, 14 Sep 2017 13:35:26 +0100
From:   James Morse <james.morse@....com>
To:     gengdongjiu <gengdongjiu@...wei.com>
CC:     christoffer.dall@...aro.org, marc.zyngier@....com,
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Subject: Re: [PATCH v6 3/7] acpi: apei: remove the unused code

Hi gengdongjiu,

On 11/09/17 13:04, gengdongjiu wrote:
> On 2017/9/9 2:17, James Morse wrote:
>> On 04/09/17 12:43, gengdongjiu wrote:
>>> On 2017/9/1 1:50, James Morse wrote:
>>>> On 28/08/17 11:38, Dongjiu Geng wrote:
>>>> If you aren't handling the notification, why is this is in the HEST at all?
>>>> (and if its not: its not firmware-first)
>>
>>> For the SEI notification, may be we can parse and handle the CPER record other than the Error physical address
>>
>> Sure, but I only see this cleanup patch in this series, where does APEI learn
>> about NOTIFY_SEI? As this is nothing will ever touch those CPER records, if
>> you're using GHESv2 firmware will be prevented from delivering subsequent
>> notifications.

> James, whether it is possible you can review the previous v5 patch which adds the support for

Spreading 'current discussion' over two versions is a problem for anyone trying
to follow this series.

If you post a newer version its normal for people to delete the older versions.
When you post a new version you should be happy that its the latest and greatest.


> NOTIFY_SEI? thanks in advancecIn that patch, I share the SEI notification
handling with the SEA
> notification handling to avoid duplicated code.

You may be able to share some of the code, but I don't think you should share
the list of GHES between notification methods.
This leads to races between the firmware and OS: If CPU-A has received an SEI
firmware would have to avoid generating an SEA on CPU-B as the SEI-handler
running on CPU-A may find and process the second set of CPER records. CPU-B then
gets a spurious notification.

Why is this a problem? KVM needs to know if APEI handled the error, or whether
the Synchronous-External-Abort/SError-Interrupt was due to something else, in
which case we invoke todays default behaviour, which isn't appropriate for a RAS
event.


Thanks,

James