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

[Alistair Popple]

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.

- 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 = {
> > 
> 
>