[Xen-devel] Fwd: XenBus_AddWatch

[hanji unit <hanjiunit@xxxxxxxxx>]

Hello, I am calling XenBus_AddWatch API from a DomU guest in the
win-pvdrivers xenpci driver, and noticed that I am not able to watch
xenstore entries that are outside of the DomU's xenstore tree. For
example, the following call in
XenPci_EvtDeviceD0EntryPostInterruptsEnabled fails with response="EIO"
even if the xenstore permissions for Container and Container/DomU in
xenstore are both "b0":

response = XenBus_AddWatch(xpdd, XN_BASE_GLOBAL, "Container/DomU",
MyCallback, xpdd);

However, the following call works and it watches a xenstore entry
relative to DomUs xenstore tree:

response = XenBus_AddWatch(xpdd, XBT_NIL, "DomU", MyCallback, xpdd);

Writing to an entry outside the DomUs tree is allowed if permissions are b0:

result = XnWriteString(xpdd, XN_BASE_GLOBAL, "Container/DomU", buffer);

It seems like DomUs should be allowed to watch xenstore entries
outside their trees. Is this a bug or is it by design?

Thanks.

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