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

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 16/10/2018 11:38, Alistair Popple wrote:
> Hi Alexey,
> 
> Looking at the skiboot side I think we only fence the NVLink bricks as part of a
> PCIe function level reset (FLR) rather than a PCI Hot or Fundamental reset which
> I believe is what the code here does. So to fence the bricks you would need to
> do either a FLR on the given link or alter Skiboot to fence a given link as part
> of a hot reset.

The code here calls OPAL to execute this code:

https://github.com/open-power/skiboot/commit/fca2b2b839a673a1e52fc6b19ee6d33b2dfbc003

This resets all links on an NPU which is fine for now as we pass GPUs in
groups only. Or I missed something?



> 
> - 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@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