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Re: [RFC for-5.1 3/4] spapr: Fix failure path for attempting to hot unpl

From: Greg Kurz
Subject: Re: [RFC for-5.1 3/4] spapr: Fix failure path for attempting to hot unplug PCI bridges
Date: Thu, 26 Mar 2020 13:18:24 +0100

On Thu, 26 Mar 2020 16:40:08 +1100
David Gibson <address@hidden> wrote:

> For various technical reasons we can't currently allow unplug a PCI to PCI
> bridge on the pseries machine.  spapr_pci_unplug_request() correctly
> generates an error message if that's attempted.
> But.. if the given errp is not error_abort or error_fatal,

Which is the always case when trying to unplug a device AFAICT:

void qdev_unplug(DeviceState *dev, Error **errp)
    DeviceClass *dc = DEVICE_GET_CLASS(dev);
    HotplugHandler *hotplug_ctrl;
    HotplugHandlerClass *hdc;
    Error *local_err = NULL;

    hdc = HOTPLUG_HANDLER_GET_CLASS(hotplug_ctrl);
    if (hdc->unplug_request) {
        hotplug_handler_unplug_request(hotplug_ctrl, dev, &local_err);

And anyway, spapr_pci_unplug_request() shouldn't rely on the caller
passing &error_fatal or &error_abort to do the right thing. Calling
error_setg() without returning right away is a dangerous practice
since it would cause a subsequent call to error_setg() with the
same errp to abort QEMU.

> it doesn't actually stop trying to unplug the bridge anyway.

This looks like a bug fix that could go to 5.0 IMHO.

Maybe add this tag ?

   Fixes: 14e714900f6b "spapr: Allow hot plug/unplug of PCI bridges and devices 
under PCI bridges"

> Signed-off-by: David Gibson <address@hidden>
> ---

Reviewed-by: Greg Kurz <address@hidden>

>  hw/ppc/spapr_pci.c | 1 +
>  1 file changed, 1 insertion(+)
> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> index 709a52780d..55ca9dee1e 100644
> --- a/hw/ppc/spapr_pci.c
> +++ b/hw/ppc/spapr_pci.c
> @@ -1663,6 +1663,7 @@ static void spapr_pci_unplug_request(HotplugHandler 
> *plug_handler,
>          if (pc->is_bridge) {
>              error_setg(errp, "PCI: Hot unplug of PCI bridges not supported");
> +            return;
>          }
>          /* ensure any other present functions are pending unplug */

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