Re: [PATCH v2 1/3] powerpc/eeh: Ignore error handlers in eeh_pe_reset_and_recover()

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Tue, Apr 26, 2016 at 08:17:31PM +1000, Gavin Shan wrote:
>On Tue, Apr 26, 2016 at 03:29:59PM +1000, David Gibson wrote:
>>On Fri, Apr 22, 2016 at 11:28:02PM +1000, Gavin Shan wrote:
>>> The function eeh_pe_reset_and_recover() is used to recover EEH
>>> error when the passthrough device are transferred to guest and
>>> backwards, meaning the device's driver is vfio-pci or none.
>>> When the driver is vfio-pci that provides error_detected() error
>>> handler only, the handler simply stops the guest and it's not
>>> expected behaviour. On the other hand, no error handlers will
>>> be called if we don't have a bound driver.
>>> 
>>> This ignores all error handlers provided by device driver in
>>> eeh_pe_reset_and_recover() to avoid the exceptional behaviour.
>>> 
>>> Fixes: 5cfb20b9 ("powerpc/eeh: Emulate EEH recovery for VFIO devices")
>>> Cc: stable@vger.kernel.org #v3.18+
>>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>> Reviewed-by: Russell Currey <ruscur@russell.cc>
>>> ---
>>>  arch/powerpc/kernel/eeh_driver.c | 11 +----------
>>>  1 file changed, 1 insertion(+), 10 deletions(-)
>>> 
>>> diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
>>> index fb6207d..1c7d703 100644
>>> --- a/arch/powerpc/kernel/eeh_driver.c
>>> +++ b/arch/powerpc/kernel/eeh_driver.c
>>> @@ -552,7 +552,7 @@ static int eeh_clear_pe_frozen_state(struct eeh_pe *pe,
>>>  
>>>  int eeh_pe_reset_and_recover(struct eeh_pe *pe)
>>>  {
>>> -	int result, ret;
>>> +	int ret;
>>>  
>>>  	/* Bail if the PE is being recovered */
>>>  	if (pe->state & EEH_PE_RECOVERING)
>>> @@ -564,9 +564,6 @@ int eeh_pe_reset_and_recover(struct eeh_pe *pe)
>>>  	/* Save states */
>>>  	eeh_pe_dev_traverse(pe, eeh_dev_save_state, NULL);
>>>  
>>> -	/* Report error */
>>> -	eeh_pe_dev_traverse(pe, eeh_report_error, &result);
>>
>>Ok, so after chatting to Gavin, I've made sense of this.  The basic
>>thing here is that eeh_pe_reset_and_recover() should be discarding any
>>errors from before the reset, not reporting them - the whole point is
>>that we know things have gone bad, and we want to clear back to a good
>>state.
>>
>>>  	/* Issue reset */
>>>  	ret = eeh_reset_pe(pe);
>>>  	if (ret) {
>>> @@ -581,15 +578,9 @@ int eeh_pe_reset_and_recover(struct eeh_pe *pe)
>>>  		return ret;
>>>  	}
>>>  
>>> -	/* Notify completion of reset */
>>> -	eeh_pe_dev_traverse(pe, eeh_report_reset, &result);
>>
>>However, it's not clear if removing the report of a reset makes sense.
>>There are no current users of reset notification IIUC, but if we're
>>going to remove the reset reporting, we should put that in a separate
>>patch with its own justification, and remove the other caller as well.
>>
>
>Thanks, David. It makes sense to me. I will split it into two: one removes
>eeh_report_error notification and another removes the left notification
>handlers.
>
>>>  	/* Restore device state */
>>>  	eeh_pe_dev_traverse(pe, eeh_dev_restore_state, NULL);
>>>  
>>> -	/* Resume */
>>> -	eeh_pe_dev_traverse(pe, eeh_report_resume, NULL);
>>
>>And I'm not sure if it makes sense to remove the resume notification either.
>>
>
>Based on the offline talk, we either keep all notification handlers or remove
>all of them. As we can't keep eeh_report_error, we have to remove all of them.
>

v3 was posted for further review. Please ignore this series.

>>>  	/* Clear recovery mode */
>>>  	eeh_pe_state_clear(pe, EEH_PE_RECOVERING);
>>>  
>>
>>-- 
>>David Gibson			| I'll have my music baroque, and my code
>>david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
>>				| _way_ _around_!
>>http://www.ozlabs.org/~dgibson
>
>