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

[Greg Kurz <groug@kaod.org>]

On Thu, 26 Mar 2020 16:40:09 +1100
David Gibson <david@gibson.dropbear.id.au> 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.
> 

This could maybe considered as a valid fix for 5.0 since this prevents
guest crashes IIUC. But since this requires the two preliminary cleanup
patches, I understand you may prefer to postpone that to 5.1.

> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---

Reviewed-by: Greg Kurz <groug@kaod.org>

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