Re: [PATCH 1/2] PCI/AER: Do not reset the device status if doing firmware first handling.

["Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>]

Hi,

On 6/17/20 2:31 AM, Jonathan Cameron wrote:
> On Tue, 16 Jun 2020 11:00:32 -0700
> "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com> wrote:
> 
>> Hi Jonathan,
>>
>> On 6/16/20 10:47 AM, Bjorn Helgaas wrote:
>>> [+cc Sathy]
>>>
>>> On Fri, May 22, 2020 at 01:31:33AM +0800, Jonathan Cameron wrote:
>>>> pci_aer_clear_device_status() currently resets the device status even when
>>>> firmware first handling is going on.  In particular it resets it on the
>>>> root port.
>>>>
>>>> This has been discussed previously
>>>> https://lore.kernel.org/patchwork/patch/427375/.
>> pci_aer_clear_device_status() is only used by handle_error_source(). And
>> I don't think handle_error_source() is called in FF mode. Can you
>> give more details on this issue ?
> 
> It's called in pcie_do_recovery
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/pci/pcie/err.c#L200
> 
> Which is called from both handle_error_source and aer_recover_work_func.
> 
> indirectly called from ghes_handle_aer / ghes_do_proc
> 
> This particular flow will only happen (I think) on hardware reduced ACPI systems.
Ok. Makes sense.
> 
> Jonathan
> 
>>>
>>> I don't think this reference is really pertinent, is it?  That patch
>>> to b2c8881da764 changes pci_cleanup_aer_uncorrect_error_status() so it
>>> doesn't clear PCI_ERR_UNCOR_STATUS in "firmware-first" mode.
>>>
>>> But your patch only affects PCI_EXP_DEVSTA, not PCI_ERR_UNCOR_STATUS.
>>>    
>>>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>>> ---
>>>>    drivers/pci/pcie/aer.c | 3 +++
>>>>    1 file changed, 3 insertions(+)
>>>>
>>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>>> index f4274d301235..43e78b97ace6 100644
>>>> --- a/drivers/pci/pcie/aer.c
>>>> +++ b/drivers/pci/pcie/aer.c
>>>> @@ -373,6 +373,9 @@ void pci_aer_clear_device_status(struct pci_dev *dev)
>>>>    {
>>>>    	u16 sta;
>>>>    
>>>> +	if (pcie_aer_get_firmware_first(dev))
use if (!pcie_aer_is_native(dev))
>>>> +		return;
>>>
>>> This needs to be adjusted because pcie_aer_get_firmware_first() no
>>> longer exists after 708b20003624 ("PCI/AER: Remove HEST/FIRMWARE_FIRST
>>> parsing for AER ownership").
>>>
>>> This will use the _OSC AER ownership bit to gate clearing of the
>>> status bits in the PCIe capability (not the AER capability).
>>>
>>> I think that's the right thing to do, but it's certainly not obvious
>>> from the _OSC description in the PCI Firmware Spec r3.2.  I think we
>>> need a pointer to the ECN that clarifies this, i.e., sec 4.5.1 of:
>>>
>>>     System Firmware Intermediary (SFI) _OSC and DPC Updates ECN, Feb 24,
>>>     2020, affecting PCI Firmware Specification, Rev. 3.2
>>>     https://members.pcisig.com/wg/PCI-SIG/document/14076
>>>    
>>>>    	pcie_capability_read_word(dev, PCI_EXP_DEVSTA, &sta);
>>>>    	pcie_capability_write_word(dev, PCI_EXP_DEVSTA, sta);
>>>>    }
>>>> -- 
>>>> 2.19.1
>>>>   
>>
> 
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer