[ +qemu-devel ] On 2021/4/30 22:29, Alex Williamson wrote: > On Fri, 30 Apr 2021 15:57:47 +0800 > Yicong Yang <yangyicong@xxxxxxxxxxxxx> wrote: > >> When I try to remove the PF driver in the host, the process will be blocked >> if the related VF of the device is added in the Qemu as an iEP. >> >> here's what I got in the host: >> >> [root@localhost 0000:75:00.0]# rmmod hisi_zip >> [99760.571352] vfio-pci 0000:75:00.1: Relaying device request to user (#0) >> [99862.992099] vfio-pci 0000:75:00.1: Relaying device request to user (#10) >> [...] >> >> and in the Qemu: >> >> estuary:/$ lspci -tv >> -[0000:00]-+-00.0 Device 1b36:0008 >> +-01.0 Device 1af4:1000 >> +-02.0 Device 1af4:1009 >> \-03.0 Device 19e5:a251 <----- the related VF device >> estuary:/$ qemu-system-aarch64: warning: vfio 0000:75:00.1: Bus 'pcie.0' does not support hotplugging >> qemu-system-aarch64: warning: vfio 0000:75:00.1: Bus 'pcie.0' does not support hotplugging >> qemu-system-aarch64: warning: vfio 0000:75:00.1: Bus 'pcie.0' does not support hotplugging >> qemu-system-aarch64: warning: vfio 0000:75:00.1: Bus 'pcie.0' does not support hotplugging >> [...] >> >> The rmmod process will be blocked until I kill the Qemu process. That's the only way if I >> want to end the rmmod. >> >> So my question is: is such block reasonable? If the VF devcie is occupied or doesn't >> support hotplug in the Qemu, shouldn't we fail the rmmod and return something like -EBUSY >> rather than make the host blocked indefinitely? > > Where would we return -EBUSY? pci_driver.remove() returns void. > Without blocking, I think our only option would be to kill the user > process. > yes. the remove() callback of pci_driver doesn't provide a way to abort the process. >> Add the VF under a pcie root port will avoid this. Is it encouraged to always >> add the VF under a pcie root port rather than directly add it as an iEP? > > Releasing a device via the vfio request interrupt is always a > cooperative process currently, the VM needs to be configured such that > the device is capable of being unplugged and the guest needs to respond > to the ejection request. Thanks, > Does it make sense to abort the VM creation and give some warnings if user try to pass a vfio pci device to the Qemu and doesn't attach it to a hotpluggable bridge? Currently I think there isn't such a mechanism in Qemu. Thanks, Yicong
