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Re: [Question] Indefinitely block in the host when remove the PF driver
From: |
Yicong Yang |
Subject: |
Re: [Question] Indefinitely block in the host when remove the PF driver |
Date: |
Tue, 11 May 2021 11:44:49 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 |
[ +qemu-devel ]
On 2021/4/30 22:29, Alex Williamson wrote:
> On Fri, 30 Apr 2021 15:57:47 +0800
> Yicong Yang <yangyicong@hisilicon.com> 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
- Re: [Question] Indefinitely block in the host when remove the PF driver,
Yicong Yang <=