Re: [External] Re: [PATCH 2/3] PCI/ERR: Clear fatal status in pcie_do_recovery()

[Zhuo Chen <chenzhuo.1@bytedance.com>]

On 9/27/22 2:09 AM, Bjorn Helgaas wrote:
> On Mon, Sep 26, 2022 at 10:01:55PM +0800, Zhuo Chen wrote:
>> 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@bytedance.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.
> 
> Good point.  In aer_root_reset(), we're updating Root Port registers,
> so I think they should look like:
> 
>    if (pcie_aer_is_native(root) && aer) {
>      ...
>    }
> 
> Does that seem safe and equivalent to you?
> 
> Bjorn

I think ‘if (aer && pcie_aer_is_native(root))’ might be safer,
because when root is NULL, 'aer' will be NUll as well, and the
predicate will return false without entering pcie_aer_is_native(root).


-- 
Thanks,
Zhuo Chen