Re: [Qemu-devel] question: disk missing in the guest contingently when hotplug several virtio scsi disks consecutively.

[l00284672]

ping


On 2018/6/27 18:33, l00284672 wrote:

Hi, I found a bug that disk missing (not all disks missing ) in the guest contingently when hotplug several virtio scsi disks consecutively.  After rebooting the guest,

the missing disks appear again.

The guest is centos7.3 running on a centos7.3 host and the scsi controllers are configed with iothread. The scsi controller xml is below:

    <controller type='scsi' index='0' model='virtio-scsi'>
      <driver iothread='26'/>
      <alias name='scsi0'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>

    </controller>
    <controller type='scsi' index='1' model='virtio-scsi'>
      <driver iothread='27'/>
      <alias name='scsi1'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>

    </controller>
    <controller type='scsi' index='2' model='virtio-scsi'>
      <driver iothread='28'/>
      <alias name='scsi2'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x0b' function='0x0'/>

    </controller>
    <controller type='scsi' index='3' model='virtio-scsi'>
      <driver iothread='29'/>
      <alias name='scsi3'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x0c' function='0x0'/>

    </controller>

If the scsi controllers are configed without iothread,  disks are all can be seen in the guest when hotplug several virtio scsi disks consecutively.

I think the biggest difference between them is that scsi controllers with iothread call virtio_notify_irqfd to notify guest and scsi controllers without

iothread call virtio_notify instead.  What make it difference? Will  interrupts are lost when call virtio_notify_irqfd due to  race condition for some

unknow reasons? Maybe guys more familiar with scsi dataplane can help. Thanks for your reply!

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