linux-kernel - Re: [PATCH 2/3] PCI/ERR: Clear fatal status in pcie_do

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Message-ID: <1de80c28-33ec-b1bd-a557-91e4166d2da7@bytedance.com>
Date:   Mon, 26 Sep 2022 22:01:55 +0800
From:   Zhuo Chen <chenzhuo.1@...edance.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     fancer.lancer@...il.com, jdmason@...zu.us, dave.jiang@...el.com,
        allenbh@...il.com, bhelgaas@...gle.com, ruscur@...sell.cc,
        oohall@...il.com, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        ntb@...ts.linux.dev, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 2/3] PCI/ERR: Clear fatal status in pcie_do_recovery()



On 9/23/22 5:08 AM, Bjorn Helgaas wrote:
> On Fri, Sep 02, 2022 at 02:16:33AM +0800, Zhuo Chen wrote:
>> When state is pci_channel_io_frozen in pcie_do_recovery(),
>> the severity is fatal and fatal status should be cleared.
>> So we add pci_aer_clear_fatal_status().
> 
> Seems sensible to me.  Did you find this by code inspection or by
> debugging a problem?  If the latter, it would be nice to mention the
> symptoms of the problem in the commit log.

I found this by code inspection so I may not enumerate what kind of 
problems this code will cause.
> 
>> Since pcie_aer_is_native() in pci_aer_clear_fatal_status()
>> and pci_aer_clear_nonfatal_status() contains the function of
>> 'if (host->native_aer || pcie_ports_native)', so we move them
>> out of it.
> 
> Wrap commit log to fill 75 columns.
> 
>> Signed-off-by: Zhuo Chen <chenzhuo.1@...edance.com>
>> ---
>>   drivers/pci/pcie/err.c | 8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 0c5a143025af..e0a8ade4c3fe 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -243,10 +243,14 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>>   	 * it is responsible for clearing this status.  In that case, the
>>   	 * signaling device may not even be visible to the OS.
>>   	 */
>> -	if (host->native_aer || pcie_ports_native) {
>> +	if (host->native_aer || pcie_ports_native)
>>   		pcie_clear_device_status(dev);
> 
> pcie_clear_device_status() doesn't check for pcie_aer_is_native()
> internally, but after 068c29a248b6 ("PCI/ERR: Clear PCIe Device Status
> errors only if OS owns AER") and aa344bc8b727 ("PCI/ERR: Clear AER
> status only when we control AER"), both callers check before calling
> it.
> 
> I think we should move the check inside pcie_clear_device_status().
> That could be a separate preliminary patch.
> 
> There are a couple other places (aer_root_reset() and
> get_port_device_capability()) that do the same check and could be
> changed to use pcie_aer_is_native() instead.  That could be another
> preliminary patch.
> 
Good suggestion. But I have only one doubt. In aer_root_reset(), if we 
use "if (pcie_aer_is_native(dev) && aer)", when dev->aer_cap
is NULL and root->aer_cap is not NULL, pcie_aer_is_native() will return 
false. It's different from just using "(host->native_aer ||
pcie_ports_native)".
Or if we can use "if (pcie_aer_is_native(root))", at this time a NULL 
pointer check should be added in pcie_aer_is_native() because root may 
be NULL.

> 
>> +	if (state == pci_channel_io_frozen)
>> +		pci_aer_clear_fatal_status(dev);
>> +	else
>>   		pci_aer_clear_nonfatal_status(dev);
>> -	}
>> +
>>   	pci_info(bridge, "device recovery successful\n");
>>   	return status;
>>   
>> -- 
>> 2.30.1 (Apple Git-130)
>>

-- 
Thanks,
Zhuo Chen