On Wed, 30 Jan 2019 16:57:31 +0100 David Hildenbrand <da...@redhat.com> wrote:
> PCI on s390x is really weird and how it was modeled in QEMU might not have > been the right choice. Anyhow, right now it is the case that: > - Hotplugging a PCI device will silently create a zPCI device > (if none is provided) > - Hotunplugging a zPCI device will unplug the PCI device (if any) > - Hotunplugging a PCI device will unplug also the zPCI device > As far as I can see, we can no longer change this behavior. But we > should fix it. > > Both device types are handled via a single hotplug handler call. This > is problematic for various reasons: > 1. Unplugging via the zPCI device allows to unplug devices that are not > hot removable. (check performed in qdev_unplug()) - bad. > 2. Hotplug handler chains are not possible for the unplug case. In the > future, the machine might want to override hotplug handlers, to > process device specific stuff and to then branch off to the actual > hotplug handler. We need separate hotplug handler calls for both the > PCI and zPCI device to make this work reliably. All other PCI > implementations are already prepared to handle this correctly, only > s390x is missing. > > Therefore, introduce the unplug_request handler and properly perform > unplug checks by redirecting to the separate unplug_request handlers. > When finally unplugging, perform two separate hotplug_handler_unplug() > calls, first for the PCI device, followed by the zPCI device. This now > nicely splits unplugging paths for both devices. > > The redirect part is a little hairy, as the user is allowed to trigger > unplug either via the PCI or the zPCI device. So redirect always to the > PCI unplug request handler first and remember if that check has been > performed in the zPCI device. Redirect then to the zPCI device unplug > request handler to perform the magic. Remembering that we already > checked the PCI device breaks the redirect loop. > > Signed-off-by: David Hildenbrand <da...@redhat.com> > --- > hw/s390x/s390-pci-bus.c | 166 +++++++++++++++++++++++++++------------- > hw/s390x/s390-pci-bus.h | 1 + > 2 files changed, 113 insertions(+), 54 deletions(-) Thanks, applied.
