Re: [RFC for-5.1 4/4] spapr: Don't allow unplug of NVLink2 devices

[David Gibson]

On Sat, Mar 28, 2020 at 11:32:18PM +1100, Alexey Kardashevskiy wrote:
> 
> 
> On 26/03/2020 16:40, David Gibson wrote:
> > Currently, we can't properly handle unplug of NVLink2 devices, because we
> > don't have code to tear down their special memory resources.  There's not
> > a lot of impetus to implement that. Since hardware NVLink2 devices can't
> > be hot unplugged, the guest side drivers don't usually support unplug
> > anyway.
> > 
> > Therefore, simply prevent unplug of NVLink2 devices.
> > 
> > Signed-off-by: David Gibson <address@hidden>
> > ---
> >  hw/ppc/spapr_pci.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 55ca9dee1e..5c8262413a 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1666,6 +1666,11 @@ static void spapr_pci_unplug_request(HotplugHandler 
> > *plug_handler,
> >              return;
> >          }
> >  
> > +        if (spapr_phb_is_nvlink_dev(pdev, phb)) {
> > +            error_setg(errp, "PCI: Cannot unplug NVLink2 devices");
> > +            return;
> > +        }
> 
> 
> Just this would do as well:
> 
> Object *po = OBJECT(pdev);
> uint64_t tgt = object_property_get_uint(po, "nvlink2-tgt", NULL);
> 
> if (tgt) {
>      error_setg(errp, "PCI: Cannot unplug NVLink2 devices");
>      return;
> }
> 
> honestly, I admin what 1/4 fixes is cryptic but since there is not going
> to be any more new nvlinkX, this does not deserve this many patches
> imho.

Good point, that is a simpler approach.

> 
>       
> 
> > +
> >          /* ensure any other present functions are pending unplug */
> >          if (PCI_FUNC(pdev->devfn) == 0) {
> >              for (i = 1; i < 8; i++) {
> > 
> 

-- 
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

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