At 03/09/2011 12:08 PM, Ryan Harper Write: > * Wen Congyang <we...@cn.fujitsu.com> [2011-02-27 20:56]: >> Hi Markus Armbruster >> >> At 02/23/2011 04:30 PM, Markus Armbruster Write: >>> Isaku Yamahata <yamah...@valinux.co.jp> writes: >>> >> >> <snip> >> >>> >>> I don't think this patch is correct. Let me explain. >>> >>> Device hot unplug is *not* guaranteed to succeed. >>> >>> For some buses, such as USB, it always succeeds immediately, i.e. when >>> the device_del monitor command finishes, the device is gone. Live is >>> good. >>> >>> But for PCI, device_del merely initiates the ACPI unplug rain dance. It >>> doesn't wait for the dance to complete. Why? The dance can take an >>> unpredictable amount of time, including forever. >>> >>> Problem: Subsequent device_add can fail if it reuses the qdev ID or PCI >>> slot, and the unplug has not yet completed (race condition), or it >>> failed. Yes, Virginia, PCI hotplug *can* fail. >>> >>> When unplug succeeds, the qdev is automatically destroyed. >>> pciej_write() does that for PIIX4. Looks like pcie_cap_slot_event() >>> does it for PCIE. >> >> I got a similar problem. When I unplug a pci device by hand, it works >> as expected, and I can hotplug it again. But when I use a srcipt to >> do the same thing, sometimes it failed. I think I may find another bug. >> >> Steps to reproduce this bug: >> 1. cat ./test-e1000.sh # RHEL6RC is domain name >> #! /bin/bash >> >> while true; do >> virsh attach-interface RHEL6RC network default --mac >> 52:54:00:1f:db:c7 --model e1000 >> if [[ $? -ne 0 ]]; then >> break >> fi >> virsh detach-interface RHEL6RC network --mac 52:54:00:1f:db:c7 >> if [[ $? -ne 0 ]]; then >> break >> fi >> sleep 5 > > How do you know that the guest has responded at this point before you > attempt to attach again at the top of the loop. Any attach/detach > requires the guest to respond to the request and it may not respond at > all.
When I attach/detach interface by hand, it works fine: I can see the new interface when I attach it, and it disapears when I detached it. > >
