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

[Alexey Kardashevskiy]

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.

        

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

-- 
Alexey