linux-kernel - Re: [PATCH] PCI: DPC: Clear AER status bits before disabling port containment

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Message-ID: <bcaa5398-3306-7b25-3d1f-d2f0568fc72a@gmail.com>
Date:   Tue, 26 Jun 2018 15:51:02 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>,
        Keith Busch <keith.busch@...el.com>
Cc:     Sinan Kaya <okaya@...eaurora.org>, bhelgaas@...gle.com,
        alex_gagniuc@...lteam.com, austin_bolen@...l.com,
        shyam_iyer@...l.com, Dongdong Liu <liudongdong3@...wei.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: DPC: Clear AER status bits before disabling port
 containment



On 06/19/2018 04:57 PM, Bjorn Helgaas wrote:
> On Wed, May 16, 2018 at 05:12:21PM -0600, Keith Busch wrote:
>> On Wed, May 16, 2018 at 06:44:22PM -0400, Sinan Kaya wrote:
>>> On 5/16/2018 5:33 PM, Alexandru Gagniuc wrote:
>>>> AER status bits are sticky, and they survive system resets. Downstream
>>>> devices are usually taken care of after re-enumerating the downstream
>>>> busses, as the AER bits are cleared during probe().
>>>>
>>>> However, nothing clears the bits of the port which contained the
>>>> error. These sticky bits may leave some BIOSes to think that something
>>>> bad happened, and print ominous messages on next boot. To prevent this,
>>>> tidy up the AER status bits before releasing containment.
>>>>
>>>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
>>>> ---
>>>>  drivers/pci/pcie/dpc.c | 4 ++++
>>>>  1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
>>>> index 8c57d607e603..bf82d6936556 100644
>>>> --- a/drivers/pci/pcie/dpc.c
>>>> +++ b/drivers/pci/pcie/dpc.c
>>>> @@ -112,6 +112,10 @@ static void dpc_work(struct work_struct *work)
>>>>  		dpc->rp_pio_status = 0;
>>>>  	}
>>>>  
>>>> +	/* DPC event made a mess of our AER status bits. Clean them up. */
>>>> +	pci_cleanup_aer_error_status_regs(pdev);
>>>> +	/* TODO: Should we also use aer_print_error to log the event? */
>>>> +
>>>>  	pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
>>>>  		PCI_EXP_DPC_STATUS_TRIGGER | PCI_EXP_DPC_STATUS_INTERRUPT);
>>>>  
>>>>
>>>
>>> I think Keith has a patch to fix this. It was under review at some point.
>>
>> Right, I do intend to following up on this, but I've had some trouble
>> finding time the last few weeks. Sorry about that, things will clear up
>> for me shortly.
> 
> I'll drop this (Alexandru's) patch for now, waiting for your update, Keith.

I wonder if clearing AER status bits is mutually exclusive with
refactoring other parts of DPC handling?

Alex