On Thu, 11 Feb 2021 19:52:41 -0300 Daniel Henrique Barboza <danielhb...@gmail.com> wrote:
> When hotunplugging a PCI function we'll branch out the logic in two cases, > function zero and non-zero. If non-zero, we'll call spapr_drc_detach() and > nothing else. If it's function zero, we'll loop it once between all the > functions in the slot to call spapr_drc_detach() on them, and afterwards > we'll do another backwards loop where we'll signal the event to the guest. > > We can simplify this logic. We can ignore all the DRC handling for non-zero > functions, since we'll end up doing that regardless when unplugging function > zero. And for function zero, everything can be done in a single loop, since > tt doesn't matter if we end up marking the function DRCs as unplug pending in > backwards order or not, as long as we call spapr_drc_detach() before issuing > the hotunplug event to the guest. > > This will also avoid a possible scenario where the user starts to hotunplug > the slot, starting with a non-zero function, and then delays/forgets to > hotunplug function zero afterwards. This would keep the function DRC marked > as unplug requested indefinitely. > ... or until the guest is reset, which will no longer happen with this patch applied, i.e. breaks the long standing policy that machine reset causes pending hot-unplug requests to succeed. I don't see an obvious reason to special case non-zero PCI functions. > Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com> > --- > hw/ppc/spapr_pci.c | 44 ++++++++++++++++---------------------------- > 1 file changed, 16 insertions(+), 28 deletions(-) > > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c > index f1c7479816..1791d98a49 100644 > --- a/hw/ppc/spapr_pci.c > +++ b/hw/ppc/spapr_pci.c > @@ -1709,38 +1709,26 @@ static void spapr_pci_unplug_request(HotplugHandler > *plug_handler, > return; > } > > - /* ensure any other present functions are pending unplug */ > - if (PCI_FUNC(pdev->devfn) == 0) { > - for (i = 1; i < 8; i++) { > - func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, > i)); > - func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc); > - state = func_drck->dr_entity_sense(func_drc); > - if (state == SPAPR_DR_ENTITY_SENSE_PRESENT > - && !spapr_drc_unplug_requested(func_drc)) { > - /* > - * Attempting to remove function 0 of a multifunction > - * device will will cascade into removing all child > - * functions, even if their unplug weren't requested > - * beforehand. > - */ > - spapr_drc_detach(func_drc); > - } > - } > + /* > + * The hotunplug itself will occur when unplugging function 0, > + * regardless of marking any other functions DRCs as pending > + * unplug beforehand (since 02a1536eee33). > + */ > + if (PCI_FUNC(pdev->devfn) != 0) { > + return; > } > > - spapr_drc_detach(drc); > + for (i = 7; i >= 0; i--) { > + func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, i)); > + func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc); > + state = func_drck->dr_entity_sense(func_drc); > > - /* if this isn't func 0, defer unplug event. otherwise signal removal > - * for all present functions > - */ > - if (PCI_FUNC(pdev->devfn) == 0) { > - for (i = 7; i >= 0; i--) { > - func_drc = drc_from_devfn(phb, chassis, PCI_DEVFN(slotnr, > i)); > - func_drck = SPAPR_DR_CONNECTOR_GET_CLASS(func_drc); > - state = func_drck->dr_entity_sense(func_drc); > - if (state == SPAPR_DR_ENTITY_SENSE_PRESENT) { > - spapr_hotplug_req_remove_by_index(func_drc); > + if (state == SPAPR_DR_ENTITY_SENSE_PRESENT) { > + /* Mark the DRC as requested unplug if needed. */ > + if (!spapr_drc_unplug_requested(func_drc)) { > + spapr_drc_detach(func_drc); > } > + spapr_hotplug_req_remove_by_index(func_drc); > } > } > }