Re: [PATCH 2/3] powerpc/pci: unmap legacy INTx interrupts of passthrough IO adapters

["Oliver O'Halloran" <oohall@gmail.com>]

On Wed, Apr 29, 2020 at 5:51 PM Cédric Le Goater <clg@kaod.org> wrote:
>
> When a passthrough IO adapter is removed from a pseries machine using
> hash MMU and the XIVE interrupt mode, the POWER hypervisor, pHyp,
> expects the guest OS to have cleared all page table entries related to
> the adapter. If some are still present, the RTAS call which isolates
> the PCI slot returns error 9001 "valid outstanding translations" and
> the removal of the IO adapter fails.
>
> INTx interrupt numbers need special care because Linux maps the
> interrupts automatically in the Linux interrupt number space if they
> are presented in the device tree node describing the IO adapter. These
> interrupts are not un-mapped automatically and in case of an hot-plug
> adapter, the PCI hot-plug layer needs to handle the cleanup to make
> sure that all the page table entries of the XIVE ESB pages are
> cleared.
>
> Cc: "Oliver O'Halloran" <oohall@gmail.com>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>  arch/powerpc/kernel/pci-hotplug.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/pci-hotplug.c b/arch/powerpc/kernel/pci-hotplug.c
> index bf83f76563a3..9e9c6befd7ea 100644
> --- a/arch/powerpc/kernel/pci-hotplug.c
> +++ b/arch/powerpc/kernel/pci-hotplug.c
> @@ -57,6 +57,8 @@ void pcibios_release_device(struct pci_dev *dev)
>         struct pci_controller *phb = pci_bus_to_host(dev->bus);
>         struct pci_dn *pdn = pci_get_pdn(dev);
>
> +       irq_dispose_mapping(dev->irq);

What does the original mapping? Powerpc arch code or the PCI core?
Tearing down the mapping in pcibios_release_device() seems a bit fishy
to me since the PCI core has already torn down the device state at
that point. If the release is delayed it's possible that another
pci_dev has mapped the IRQ before we get here, but maybe that's ok.

> +
>         eeh_remove_device(dev);
>
>         if (phb->controller_ops.release_device)
> --
> 2.25.4
>