Re: [PATCH] PCI: pciehp: Fix re-enabling the slot marked for safe removal

[Sergey Miroshnichenko <s.miroshnichenko@yadro.com>]

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On 3/5/19 2:01 PM, Lukas Wunner wrote:
> On Fri, Mar 01, 2019 at 07:12:51PM +0300, Sergey Miroshnichenko wrote:
>> During the safe removal procedure, a Data Link Layer State Changed event
>> may occur after pciehp_power_off_slot(), and it is handled when the slot is
>> already set to OFF_STATE. This results in re-enabling the device and makes
>> it impossible to actually safely remove it.
>>
>> Add a check for a Presence Detect Changed bit to filter out this interrupt.
>>
>> It is still possible to re-enable the device if it remains in the slot
>> after pressing the Attention Button by pressing it again.
>>
>> Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko@yadro.com>
>> Cc: Lukas Wunner <lukas@wunner.de>
>> ---
>>  drivers/pci/hotplug/pciehp_ctrl.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
>> index 3f3df4c29f6e..941f77b71df4 100644
>> --- a/drivers/pci/hotplug/pciehp_ctrl.c
>> +++ b/drivers/pci/hotplug/pciehp_ctrl.c
>> @@ -251,6 +251,14 @@ void pciehp_handle_presence_or_link_change(struct controller *ctrl, u32 events)
>>  		return;
>>  	}
>>  
>> +	/* Handle the DLLSC from the slot which just has been turned off */
>> +	if ((events & PCI_EXP_SLTSTA_DLLSC) &&
>> +	    !(events & PCI_EXP_SLTSTA_PDC) &&
>> +	    present && !link_active) {
>> +		mutex_unlock(&ctrl->state_lock);
>> +		return;
>> +	}
>> +
>>  	switch (ctrl->state) {
>>  	case BLINKINGON_STATE:
>>  		cancel_delayed_work(&ctrl->button_work);
> 
> Hm, I'd instead prefer amending remove_board() like this:
> 
>  	if (POWER_CTRL(ctrl)) {
>  		pciehp_power_off_slot(ctrl);
>  
>  		/*
>  		 * After turning power off, we must wait for at least 1 second
>  		 * before taking any action that relies on power having been
>  		 * removed from the slot/adapter.
>  		 */
>  		msleep(1000);
>  
> +		/* ignore link or presence changes caused by power off */
> +		atomic_and(~(PCI_EXP_SLTSTA_DLLSC | PCI_EXP_SLTSTA_PDC),
> +			   &ctrl->pending_events);
>  	}
> 
> Would this work for you?

Thank you for the review and for the proposed change! This discards
exactly the event which caused the issue - I've just checked it on our
hardware, and will resend it as a v2.

Best regards,
Serge

> 
> Thanks,
> 
> Lukas
> 


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