Signed-off-by: Olaf Hering
Acked-by: Ian Campbell
Cc: Ian Campbell
Cc: Ian Jackson
Cc: Jan Beulich
Cc: Keir Fraser
Cc: Tim Deegan
---
xen/include/public/io/vscsiif.h | 68 +
1 file changed, 68 insertions(+)
diff --git a/xen/include/public/io/vscsiif.h b/xen/include/public/io/vscsiif.h
index e8e38a9..2c5f04a 100644
--- a/xen/include/public/io/vscsiif.h
+++ b/xen/include/public/io/vscsiif.h
@@ -104,6 +104,74 @@
* response structures.
*/
+/*
+ * Xenstore format in practice
+ * ===
+ *
+ * The backend driver uses a single_host:many_devices notation to manage domU
+ * devices. Everything is stored in
/local/domain//backend/vscsi/.
+ * The xenstore layout looks like this (dom0 is assumed to be the
backend_domid):
+ *
+ * //feature-host = "0"
+ * //frontend = "/local/domain//device/vscsi/0"
+ * //frontend-id = ""
+ * //online = "1"
+ * //state = "4"
+ * //vscsi-devs/dev-0/p-dev = "8:0:2:1" or "naa.wwn:lun"
+ * //vscsi-devs/dev-0/state = "4"
+ * //vscsi-devs/dev-0/v-dev = "0:0:0:0"
+ * //vscsi-devs/dev-1/p-dev = "8:0:2:2"
+ * //vscsi-devs/dev-1/state = "4"
+ * //vscsi-devs/dev-1/v-dev = "0:0:1:0"
+ *
+ * The frontend driver maintains its state in
+ * /local/domain//device/vscsi/.
+ *
+ * /backend = "/local/domain/0/backend/vscsi//"
+ * /backend-id = "0"
+ * /event-channel = "20"
+ * /ring-ref = "43"
+ * /state = "4"
+ * /vscsi-devs/dev-0/state = "4"
+ * /vscsi-devs/dev-1/state = "4"
+ *
+ * In addition to the entries for backend and frontend these flags are stored
+ * for the toolstack:
+ *
+ * //vscsi-devs/dev-1/p-devname = "/dev/$device"
+ *
+ *
+ * Backend/frontend protocol
+ * =
+ *
+ * To create a vhost along with a device:
+ * //feature-host = "0"
+ * //frontend = "/local/domain//device/vscsi/0"
+ * //frontend-id = ""
+ * //online = "1"
+ * //state = "1"
+ * //vscsi-devs/dev-0/p-dev = "8:0:2:1"
+ * //vscsi-devs/dev-0/state = "1"
+ * //vscsi-devs/dev-0/v-dev = "0:0:0:0"
+ * Wait for //state + //vscsi-devs/dev-0/state
become 4
+ *
+ * To add another device to a vhost:
+ * //state = "7"
+ * //vscsi-devs/dev-1/p-dev = "8:0:2:2"
+ * //vscsi-devs/dev-1/state = "1"
+ * //vscsi-devs/dev-1/v-dev = "0:0:1:0"
+ * Wait for //state + //vscsi-devs/dev-1/state
become 4
+ *
+ * To remove a device from a vhost:
+ * //state = "7"
+ * //vscsi-devs/dev-1/state = "5"
+ * Wait for //state to become 4
+ * Wait for //vscsi-devs/dev-1/state become 6
+ * Remove //vscsi-devs/dev-1/{state,p-dev,v-dev,p-devname}
+ * Remove //vscsi-devs/dev-1/
+ *
+ */
+
/* Requests from the frontend to the backend */
/*
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