[Xen-devel] Fwd: vTPM should be detached after being destroyed

[Emil Condrea <emilcondrea@xxxxxxxxx>]

I see that when the vTPM domain is destroyed using xl destroy the advertised info is not removed from xenstore. I don't see a reason for which it should remain there.Â

If something crashes the vTPM it must be destroyed, started again and attached to domU using xl vtpm-attach. The problem is that because the previous vTPM was not removed from xenstore, the new one will be seen different in domU, instead of vtpm0 it will see both vtpm0(unusable) and vtpm1(working).

For the moment, doing a vtpm-detach before attaching the new vtpm allows the guest to see the correct vtpm but since vtpm0 will not be usable anymore why not cleaning stuff on destroy?

Is there something that I miss? Also, I have some errors while running xl destroy vtpm and maybe this affects correct cleaning:

xl -vvv destroy vtpm also warns thatÂ

backend /local/domain/...vtpm/../state wanted state 6 but it was removed. I see from devstate_watch_callback that this error happens when it could not find some info in the xenstore.Â

It is there a synchronization problem and some xenstore info is deleted too soon and then the destroy operation fails?

After this step, the error is sent to the calling functions:

libxl_device.c:device_backend_callback: unable to remove device with path /local/domain/...vtpm/58/0

libxl.c:devices_destroy_cb:libxl__devices_destroy failed for 58

What do you think? Is it a good ideea to detach vtpm on destroy? Should I send a patch with the changes?Â

Thanks.

Emil Condrea

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel