Hi Juergen,
On 27/05/2022 08:24, Juergen Gross wrote:
Add documentation for two new Xenstore wire commands SET_FEATURE and
GET_FEATURE used to set or query the Xenstore features visible in the
ring page of a given domain.
Signed-off-by: Juergen Gross <jgr...@suse.com>
---
Do we need support in the migration protocol for the features?
I would say yes. You want to make sure that the client can be migrated
without loosing features between two xenstored.
V2:
- remove feature bit (Julien Grall)
- GET_FEATURE without domid will return Xenstore supported features
(triggered by Julien Grall)
---
docs/misc/xenstore.txt | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
index a3d3da0a5b..00f6969202 100644
--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -331,6 +331,20 @@ SET_TARGET <domid>|<tdomid>|
xenstored prevents the use of SET_TARGET other than by dom0.
+GET_FEATURE [<domid>|] <value>|
+SET_FEATURE <domid>|<value>|
+ Returns or sets the contents of the "feature" field located at
+ offset 2064 of the Xenstore ring page of the domain specified by
+ <domid>. <value> is a decimal number being a logical or of the
In the context of migration, I am stilll a bit concerned that the
features are stored in the ring because the guest could overwrite it.
I would expect the migration code to check that the GET_FEATURE <domid>
is a subset of GET_FEATURE on the targeted Xenstored. So it can easily
prevent a guest to migrate.
So I think this should be a shadow copy that will be returned instead of
the contents of the "feature" field.
+ feature bits as defined in docs/misc/xenstore-ring.txt. Trying
+ to set a bit for a feature not being supported by the running
+ Xenstore will be denied. Providing no <domid> with the
+ GET_FEATURE command will return the features which are supported
+ by Xenstore.
Do we want to allow modifying the features when the guest is running?
+
+ xenstored prevents the use of GET_FEATURE and SET_FEATURE other
+ than by dom0.
Cheers,
--
Julien Grall
