On Thu, 22 Oct 2020 08:06:55 -0400 "Michael S. Tsirkin" wrote: > On Thu, Oct 22, 2020 at 02:40:26PM +0300, Marcel Apfelbaum wrote: > > From: Marcel Apfelbaum > > > > During PCIe Root Port's transition from Power-Off to Power-ON (or vice-versa) > > the "Slot Control Register" has the "Power Indicator Control" > > set to "Blinking" expressing a "power transition" mode. > > > > Any hotplug operation during the "power transition" mode is not permitted > > or at least not expected by the Guest OS leading to strange failures. > > > > Detect and refuse hotplug operations in such case. > > > > Signed-off-by: Marcel Apfelbaum > > --- > > hw/pci/pcie.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c > > index 5b48bae0f6..2fe5c1473f 100644 > > --- a/hw/pci/pcie.c > > +++ b/hw/pci/pcie.c > > @@ -410,6 +410,7 @@ void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev, > > PCIDevice *hotplug_pdev = PCI_DEVICE(hotplug_dev); > > uint8_t *exp_cap = hotplug_pdev->config + hotplug_pdev->exp.exp_cap; > > uint32_t sltcap = pci_get_word(exp_cap + PCI_EXP_SLTCAP); > > + uint32_t sltctl = pci_get_word(exp_cap + PCI_EXP_SLTCTL); > > > > /* Check if hot-plug is disabled on the slot */ > > if (dev->hotplugged && (sltcap & PCI_EXP_SLTCAP_HPC) == 0) { > > @@ -418,6 +419,12 @@ void pcie_cap_slot_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev, > > return; > > } > > > > + if ((sltctl & PCI_EXP_SLTCTL_PIC) == PCI_EXP_SLTCTL_PWR_IND_BLINK) { > > + error_setg(errp, "Hot-plug failed: %s is in Power Transition", > > + DEVICE(hotplug_pdev)->id); > > + return; > > + } > > + > > pcie_cap_slot_plug_common(PCI_DEVICE(hotplug_dev), dev, errp); > > } > > Probably the only way to handle for existing machine types. > For new ones, can't we queue it in host memory somewhere? I'm not actually convinced we can't do that even for existing machine types. So I'm a bit hesitant to suggest going ahead with this without looking a bit closer at whether we can implement a wait-for-ready in qemu, rather than forcing every user of qemu (human or machine) to do so. -- David Gibson Principal Software Engineer, Virtualization, Red Hat