Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org A4CE06021C
Subject: Re: [PATCH] PCI/AER: don't call recovery process for correctable
 errors
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     bhelgaas@google.com, jonathan.derrick@intel.com,
        keith.busch@intel.com, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <1503940184-29423-1-git-send-email-tbaicar@codeaurora.org>
 <20171002231903.GE5407@bhelgaas-glaptop.roam.corp.google.com>
 <ef205683-9254-8583-7351-7264faec567a@codeaurora.org>
 <20171011170946.GI25517@bhelgaas-glaptop.roam.corp.google.com>
From:   Tyler Baicar <tbaicar@codeaurora.org>
Message-ID: <f1e80ad1-8e08-c96c-db03-64efd4a6f245@codeaurora.org>
Date:   Tue, 7 Nov 2017 18:27:03 -0500
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.4.0
MIME-Version: 1.0
In-Reply-To: <20171011170946.GI25517@bhelgaas-glaptop.roam.corp.google.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/11/2017 1:09 PM, Bjorn Helgaas wrote:
> On Wed, Oct 11, 2017 at 10:37:47AM -0400, Tyler Baicar wrote:
>> On 10/2/2017 7:19 PM, Bjorn Helgaas wrote:
>>> On Mon, Aug 28, 2017 at 11:09:44AM -0600, Tyler Baicar wrote:
>>>> Correctable errors do not need any software intervention, so
>>>> avoid calling into the software recovery process for correctable
>>>> errors.
>>>>
>>>> Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
>>>> ---
>>>>   drivers/pci/pcie/aer/aerdrv_core.c | 3 ++-
>>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
>>>> index b1303b3..4765c11 100644
>>>> --- a/drivers/pci/pcie/aer/aerdrv_core.c
>>>> +++ b/drivers/pci/pcie/aer/aerdrv_core.c
>>>> @@ -626,7 +626,8 @@ static void aer_recover_work_func(struct work_struct *work)
>>>>   			continue;
>>>>   		}
>>>>   		cper_print_aer(pdev, entry.severity, entry.regs);
>>>> -		do_recovery(pdev, entry.severity);
>>>> +		if (entry.severity != AER_CORRECTABLE)
>>>> +			do_recovery(pdev, entry.severity);
>>> I think this is fine, and it mirrors what is done in
>>> handle_error_source().
>>>
>>> But I want to converge the APEI path and the "native" AER path, so as
>>> one tiny step in that direction, can you look into doing this test
>>> once, e.g., move the test from handle_error_source() into
>>> do_recovery(), where one test will handle both paths?
>> I've looked into this and it seems there is still going to need to
>> be two versions of this check. The native AER path goes through
>> handle_error_source() and for correctable errors requires the write
>> to PCI_ERR_COR_STATUS, but the APEI path does not require this
>> write. I could move this check to the beginning of do_recovery() so
>> it returns right away for correctable errors and remove the else
>> line in handle_error_source() so it always calls into do_recovery().
>> That doesn't seem like a very clean solution though since then there
>> are still two checks for correctable errors and now we're calling
>> into do_recovery() in both cases for nothing :)
> The PCI_ERR_COR_STATUS thing is part of what I see as the problem
> here.  IMHO, the native AER path should collect up the log registers
> (and do any acknowledgement, e.g., writing PCI_ERR_COR_STATUS)
> *before* entering the common path.
>
> In other words, the Linux code in the native part of AER should be
> functionally the same as the BIOS code that implements the APEI path.
>
> This is a bit of restructuring in the Linux AER code.  I haven't
> looked enough to know how much.  If it's impractical, it's
> impractical.  I thought this might be an opportunity for a tiny step
> in that direction, but if it's not, I guess that's OK.
Hello Bjorn,

That restructuring doesn't look trivial to do in this patch, so do you think 
this patch is
good for 4.15?

Thanks,
Tyler

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.


From 1580981930276887857@xxx Wed Oct 11 17:11:01 +0000 2017
X-GM-THRID: 1576995657442027352
X-Gmail-Labels: Inbox,Category Forums