Hi Everyone,
We want to add extra options to device xml to skip reattach of pci passthrough
devices. Following is xml format for pci passthrough devices added to domain as
of now.
<hostdev mode='subsystem' type='pci' managed='yes'>
<source>
<address domain='0x0000' bus='0x00' slot='0x1a' function='0x7'/>
</source>
</hostdev>
When we pass managed=’yes’ flag through xml, libvirt takes responsibility of
detaching device on domain(guest VM) start and reattaching on domain shutdown.
We observed some issues where guest VM shutdown may take long time, blocked for
reattach operation on pci passthrough device. As domain lock is held during
this time it also makes libvirt mostly inactive as it blocks even basic
operations like (virsh list). Reattaching of device to host can block due to
reasons like buggy driver or initialization of device itself can take long time
in some cases.
We want to pass following extra options to resolve this:
1. skipReAttach (optional flag)
In some cases we do not need to reattach device to host as it may be reserved
only for guests, with this flag we can skip reattach operation on host. We do
not want to modify managed flag to avoid regression, so thinking of adding new
optional flag.
1. reAttachDriverName (optional flag)
Name of driver to which we want to attach instead of default, to avoid
reattaching to buggy driver. Currently libvirt asks host to auto selects driver
for device.
Yes we can use managed=’no’ but in that case user has to take responsibility of
detaching device before starting domain which we do not want. Please let us
know your views on this.
Thanks
Manish Mishra
