Re: [Question] Indefinitely block in the host when remove the PF driver
From: Alex Williamson
Date: Fri Apr 30 2021 - 10:29:51 EST
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.
> 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,
Alex