Re: [Xen-devel] Permission for xenstore operation on HVM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-09-21 at 03:22 +0100, duolvxendev wrote:
> I'm trying to create a directory and write some messages, i.e. to some path
> like /local/domain/$DOMID/my_directory/my_key. This is OK on pv domU, but
> denied on HVM.

There is no deliberate difference between PV and HVM and indeed:
# ./xen-detect 
Running in PV context on Xen v4.2.
# xenstore-write my_directory/my_key "foo"
xenstore-write: could not write path my_directory/my_key

even if I use dom0 tools to get the domid:
# xenstore-write /local/domain/413/my_directory/my_key "foo"
xenstore-write: could not write path /local/domain/413/my_directory/my_key

If you use one of the xs areas set aside for guest use then this works. e.g.
# xenstore-write data/foo "test"

>  I can write to /local/domain/device directory by frontend
> driver, but I cannot create or write to some arbitrary path that doesn't
> exist.

Correct, the locations which a guest can write to are deliberately
restricted as explained by Stefano.

Ian.

>  It looks like that one needs special permission on HVM.
> 
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> 
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