[PATCH kernel v2] powerpc/ioda/npu: Call skiboot's hot reset hook when disabling NPU2

[Alexey Kardashevskiy]

On 16/10/2018 13:19, Alistair Popple wrote:
>> reset_ntl() does what npu2_dev_procedure_reset() does plus more stuff,
>> there nothing really in npu2_dev_procedure_reset() which reset_ntl()
>> does not do already from the hardware standpoint. And it did stop HMIs
>> for me though.
>>
>> but ok, what will be sufficient then if not reset_ntl()?
> 
> Argh, yes you are correct. Specifically both npu2_dev_procedure_reset() and
> reset_ntl() contain:
> 
> 	/* NTL Reset */
> 	val = npu2_read(ndev->npu, NPU2_NTL_MISC_CFG1(ndev));
> 	val |= PPC_BIT(8) | PPC_BIT(9);
> 	npu2_write(ndev->npu, NPU2_NTL_MISC_CFG1(ndev), val);
> 
> Which should fence the brick. However from what I recall there was more to
> reliably preventing HMIs than merely fencing the brick. It invovled a sequence
> of fencing and flushing the cache with dcbf instructions at the right time which
> is why we also have the FLR. Unfortunately I don't know the precise details,
> perhaps if we send enough coffee Balbir's way he might be able remind us?


He suggested and ack'ed that skiboot patch, I can repeat beers^wcoffee
but it won't change much ;)



> 
> - Alistair
> 
>>
>>
>>>
>>> - Alistair
>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> - Alistair
>>>>>
>>>>> On Monday, 15 October 2018 6:17:51 PM AEDT Alexey Kardashevskiy wrote:
>>>>>> Ping?
>>>>>>
>>>>>>
>>>>>> On 02/10/2018 13:20, Alexey Kardashevskiy wrote:
>>>>>>> The skiboot firmware has a hot reset handler which fences the NVIDIA V100
>>>>>>> GPU RAM on Witherspoons and makes accesses no-op instead of throwing HMIs:
>>>>>>> https://github.com/open-power/skiboot/commit/fca2b2b839a67
>>>>>>>
>>>>>>> Now we are going to pass V100 via VFIO which most certainly involves
>>>>>>> KVM guests which are often terminated without getting a chance to offline
>>>>>>> GPU RAM so we end up with a running machine with misconfigured memory.
>>>>>>> Accessing this memory produces hardware management interrupts (HMI)
>>>>>>> which bring the host down.
>>>>>>>
>>>>>>> To suppress HMIs, this wires up this hot reset hook to vfio_pci_disable()
>>>>>>> via pci_disable_device() which switches NPU2 to a safe mode and prevents
>>>>>>> HMIs.
>>>>>>>
>>>>>>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>>>>>>> ---
>>>>>>> Changes:
>>>>>>> v2:
>>>>>>> * updated the commit log
>>>>>>> ---
>>>>>>>  arch/powerpc/platforms/powernv/pci-ioda.c | 10 ++++++++++
>>>>>>>  1 file changed, 10 insertions(+)
>>>>>>>
>>>>>>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>>>> index cde7102..e37b9cc 100644
>>>>>>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>>>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>>>>>> @@ -3688,6 +3688,15 @@ static void pnv_pci_release_device(struct pci_dev *pdev)
>>>>>>>  		pnv_ioda_release_pe(pe);
>>>>>>>  }
>>>>>>>  
>>>>>>> +static void pnv_npu_disable_device(struct pci_dev *pdev)
>>>>>>> +{
>>>>>>> +	struct eeh_dev *edev = pci_dev_to_eeh_dev(pdev);
>>>>>>> +	struct eeh_pe *eehpe = edev ? edev->pe : NULL;
>>>>>>> +
>>>>>>> +	if (eehpe && eeh_ops && eeh_ops->reset)
>>>>>>> +		eeh_ops->reset(eehpe, EEH_RESET_HOT);
>>>>>>> +}
>>>>>>> +
>>>>>>>  static void pnv_pci_ioda_shutdown(struct pci_controller *hose)
>>>>>>>  {
>>>>>>>  	struct pnv_phb *phb = hose->private_data;
>>>>>>> @@ -3732,6 +3741,7 @@ static const struct pci_controller_ops pnv_npu_ioda_controller_ops = {
>>>>>>>  	.reset_secondary_bus	= pnv_pci_reset_secondary_bus,
>>>>>>>  	.dma_set_mask		= pnv_npu_dma_set_mask,
>>>>>>>  	.shutdown		= pnv_pci_ioda_shutdown,
>>>>>>> +	.disable_device		= pnv_npu_disable_device,
>>>>>>>  };
>>>>>>>  
>>>>>>>  static const struct pci_controller_ops pnv_npu_ocapi_ioda_controller_ops = {
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
> 
> 

-- 
Alexey