linux-kernel - Re: [PATCH] acpi: apei: clear error status before acknowledging the error

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Message-ID: <82fe23f6-efd8-d256-7f34-a0bbc91237d3@codeaurora.org>
Date:   Thu, 3 Aug 2017 16:06:22 -0600
From:   "Baicar, Tyler" <tbaicar@...eaurora.org>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Borislav Petkov <bp@...e.de>, rjw@...ysocki.net, lenb@...nel.org,
        will.deacon@....com, james.morse@....com, shiju.jose@...wei.com,
        geliangtang@...il.com, andriy.shevchenko@...ux.intel.com,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi: apei: clear error status before acknowledging the
 error

On 7/31/2017 11:44 AM, Baicar, Tyler wrote:
> On 7/31/2017 11:00 AM, Luck, Tony wrote:
>> On Mon, Jul 31, 2017 at 10:15:27AM -0600, Baicar, Tyler wrote:
>>> I think the better thing to do in this case is still send the ack. If
>>> ghes_read_estatus() fails, then
>>> either we are unable to read the estatus or the estatus is 
>>> empty/invalid.
>> Right now we silently handle that failure of ghes_read_estatus(). That
>> might be hiding some Linux bugs if we are calling ghes_proc() in cases
>> where we shouldn't.
>>
>> Perhaps we should have something like this, so if systems do start 
>> acting
>> weirdly there will be a note that we took this path:
>>
>>     rc = ghes_read_estatus(ghes, 0);
>>     if (rc) {
>>         pr_notice("surprise failure reading ghes estatus\n");
>>         goto out;
>>     }
> Thank you Tony for the feedback, I can add a print like this in the 
> next version. I'll verify that
> rc is not -ENOENT though so we don't print it on empty scenarios since 
> the polled source
> will be hitting this path frequently.
>
Hi Tony,

I think I'm going to avoid adding this print, the failures are reported 
in prints in ghes_read_estatus(), so it looks a little redundant:

[  133.601165] [Firmware Warn]: GHES: Failed to read error status block!
[  133.601167] surprise failure reading GHES estatus

Thanks,
Tyler
>>
>>> If we do not send the ack, then we will be in a scenario where FW 
>>> will not
>>> send any more errors.
>> We might ACK something that the firmware didn't send, which may
>> lead to other problems.
>>
>>> I think it would be better to still have the FW send the errors and 
>>> kernel
>>> complain about issues with
>> But I agree with this. We should send the ACK.  Luckliy this doesn't 
>> have
>> a long legacy problem because the whole ACK mechanism is a new thing. So
>> we only have to worry about GHESv2 supporting BIOS.
>>
>> -Tony
>

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