Re: [PATCH v4] PCI: Prevent power state transition of erroneous device

[Mario Limonciello <superm1@kernel.org>]

On 5/20/2025 10:47 AM, Raag Jadav wrote:
> On Tue, May 20, 2025 at 10:23:57AM -0500, Mario Limonciello wrote:
>> On 5/20/2025 4:48 AM, Raag Jadav wrote:
>>> On Mon, May 19, 2025 at 11:42:31PM +0200, Denis Benato wrote:
>>>> On 5/19/25 12:41, Raag Jadav wrote:
>>>>> On Mon, May 19, 2025 at 03:58:08PM +0530, Raag Jadav wrote:
>>>>>> If error status is set on an AER capable device, most likely either the
>>>>>> device recovery is in progress or has already failed. Neither of the
>>>>>> cases are well suited for power state transition of the device, since
>>>>>> this can lead to unpredictable consequences like resume failure, or in
>>>>>> worst case the device is lost because of it. Leave the device in its
>>>>>> existing power state to avoid such issues.
>>>>>>
>>>>>> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
>>>>>> ---
>>>>>>
>>>>>> v2: Synchronize AER handling with PCI PM (Rafael)
>>>>>> v3: Move pci_aer_in_progress() to pci_set_low_power_state() (Rafael)
>>>>>>       Elaborate "why" (Bjorn)
>>>>>> v4: Rely on error status instead of device status
>>>>>>       Condense comment (Lukas)
>>>>> Since pci_aer_in_progress() is changed I've not included Rafael's tag with
>>>>> my understanding of this needing a revisit. If this was a mistake, please
>>>>> let me know.
>>>>>
>>>>> Denis, Mario, does this fix your issue?
>>>>>
>>>> Hello,
>>>>
>>>> Unfortunately no, I have prepared a dmesg but had to remove the bootup process because it was too long of a few kb: https://pastebin.com/1uBEA1FL
>>>
>>> Thanks for the test. It seems there's no hotplug event this time around
>>> and endpoint device is still intact without any PCI related failure.
>>>
>>> Also,
>>>
>>> amdgpu 0000:09:00.0: PCI PM: Suspend power state: D3hot
>>>
>>> Which means whatever you're facing is either not related to this patch,
>>> or at best exposed some nasty side-effect that's not handled correctly
>>> by the driver.
>>>
>>> I'd say amdgpu folks would be of better help for your case.
>>>
>>> Raag
>>
>> So according to the logs Denis shared with v4
>> (https://pastebin.com/1uBEA1FL) the GPU should have been going to BOCO. This
>> stands for "Bus off Chip Off"
>>
>> amdgpu 0000:09:00.0: amdgpu: Using BOCO for runtime pm
>>
>> If it's going to D3hot - that's not going to be BOCO, it should be going to
>> D3cold.
> 
> Yes, because upstream port is in D0 for some reason (might be this patch
> but not sure) and so will be the root port.
> 
> pcieport 0000:07:00.0: PCI PM: Suspend power state: D0
> pcieport 0000:07:00.0: PCI PM: Skipped
> 
> and my best guess is the driver is not able to cope with the lack of D3cold.

Yes; if the driver is configured to expect BOCO (D3cold) if it doesn't 
get it, chaos ensues.

I guess let's double check the behavior with CONFIG_PCI_DEBUG to verify 
this patch is what is changing that upstream port behavior.

> 
> Raag
> 
>> Denis, can you redo your logs with out Raag's patch patch and set
>> CONFIG_PCI_DEBUG to compare?  The 6.14.6 log you shared already
>> (https://pastebin.com/kLZtibcD) also chooses BOCO but I'm suspecting picks
>> D3cold like it should.
>>
>>>
>>>>>> More discussion on [1].
>>>>>> [1] https://lore.kernel.org/all/CAJZ5v0g-aJXfVH+Uc=9eRPuW08t-6PwzdyMXsC6FZRKYJtY03Q@mail.gmail.com/
>>>>>>
>>>>>>    drivers/pci/pci.c      |  9 +++++++++
>>>>>>    drivers/pci/pcie/aer.c | 13 +++++++++++++
>>>>>>    include/linux/aer.h    |  2 ++
>>>>>>    3 files changed, 24 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>>>>>> index 4d7c9f64ea24..a20018692933 100644
>>>>>> --- a/drivers/pci/pci.c
>>>>>> +++ b/drivers/pci/pci.c
>>>>>> @@ -9,6 +9,7 @@
>>>>>>     */
>>>>>>    #include <linux/acpi.h>
>>>>>> +#include <linux/aer.h>
>>>>>>    #include <linux/kernel.h>
>>>>>>    #include <linux/delay.h>
>>>>>>    #include <linux/dmi.h>
>>>>>> @@ -1539,6 +1540,14 @@ static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state, bool
>>>>>>    	   || (state == PCI_D2 && !dev->d2_support))
>>>>>>    		return -EIO;
>>>>>> +	/*
>>>>>> +	 * If error status is set on an AER capable device, it is not well
>>>>>> +	 * suited for power state transition. Leave it in its existing power
>>>>>> +	 * state to avoid issues like unpredictable resume failure.
>>>>>> +	 */
>>>>>> +	if (pci_aer_in_progress(dev))
>>>>>> +		return -EIO;
>>>>>> +
>>>>>>    	pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>>>>>>    	if (PCI_POSSIBLE_ERROR(pmcsr)) {
>>>>>>    		pci_err(dev, "Unable to change power state from %s to %s, device inaccessible\n",
>>>>>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>>>>>> index a1cf8c7ef628..617fbac0d38a 100644
>>>>>> --- a/drivers/pci/pcie/aer.c
>>>>>> +++ b/drivers/pci/pcie/aer.c
>>>>>> @@ -237,6 +237,19 @@ int pcie_aer_is_native(struct pci_dev *dev)
>>>>>>    }
>>>>>>    EXPORT_SYMBOL_NS_GPL(pcie_aer_is_native, "CXL");
>>>>>> +bool pci_aer_in_progress(struct pci_dev *dev)
>>>>>> +{
>>>>>> +	int aer = dev->aer_cap;
>>>>>> +	u32 cor, uncor;
>>>>>> +
>>>>>> +	if (!pcie_aer_is_native(dev))
>>>>>> +		return false;
>>>>>> +
>>>>>> +	pci_read_config_dword(dev, aer + PCI_ERR_COR_STATUS, &cor);
>>>>>> +	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_STATUS, &uncor);
>>>>>> +	return cor || uncor;
>>>>>> +}
>>>>>> +
>>>>>>    static int pci_enable_pcie_error_reporting(struct pci_dev *dev)
>>>>>>    {
>>>>>>    	int rc;
>>>>>> diff --git a/include/linux/aer.h b/include/linux/aer.h
>>>>>> index 02940be66324..e6a380bb2e68 100644
>>>>>> --- a/include/linux/aer.h
>>>>>> +++ b/include/linux/aer.h
>>>>>> @@ -56,12 +56,14 @@ struct aer_capability_regs {
>>>>>>    #if defined(CONFIG_PCIEAER)
>>>>>>    int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
>>>>>>    int pcie_aer_is_native(struct pci_dev *dev);
>>>>>> +bool pci_aer_in_progress(struct pci_dev *dev);
>>>>>>    #else
>>>>>>    static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
>>>>>>    {
>>>>>>    	return -EINVAL;
>>>>>>    }
>>>>>>    static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
>>>>>> +static inline bool pci_aer_in_progress(struct pci_dev *dev) { return false; }
>>>>>>    #endif
>>>>>>    void pci_print_aer(struct pci_dev *dev, int aer_severity,
>>>>>> -- 
>>>>>> 2.34.1
>>>>>>
>>