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[PATCH v6 3/7] docs/features/dom0less: Update the late XenStore init protocol


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  • From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
  • Date: Thu, 6 Feb 2025 17:53:37 -0800
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  • Cc: <sstabellini@xxxxxxxxxx>, <bertrand.marquis@xxxxxxx>, <julien@xxxxxxx>, <michal.orzel@xxxxxxx>, <Volodymyr_Babchuk@xxxxxxxx>, Henry Wang <xin.wang2@xxxxxxx>
  • Delivery-date: Fri, 07 Feb 2025 01:53:55 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

From: Henry Wang <xin.wang2@xxxxxxx>

With the new allocation strategy of Dom0less DomUs XenStore page,
update the doc of the late XenStore init protocol accordingly.

Signed-off-by: Henry Wang <xin.wang2@xxxxxxx>
---
 docs/features/dom0less.pandoc | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/docs/features/dom0less.pandoc b/docs/features/dom0less.pandoc
index 725afa0558..8b178edee0 100644
--- a/docs/features/dom0less.pandoc
+++ b/docs/features/dom0less.pandoc
@@ -110,9 +110,10 @@ hotplug PV drivers to dom0less guests. E.g. xl 
network-attach domU.
 The implementation works as follows:
 - Xen allocates the xenstore event channel for each dom0less domU that
   has the "xen,enhanced" property, and sets HVM_PARAM_STORE_EVTCHN
-- Xen does *not* allocate the xenstore page and sets HVM_PARAM_STORE_PFN
-  to ~0ULL (invalid)
-- Dom0less domU kernels check that HVM_PARAM_STORE_PFN is set to invalid
+- Xen allocates the xenstore page and sets HVM_PARAM_STORE_PFN as well
+  as the connection status to XENSTORE_RECONNECT.
+- Dom0less domU kernels check that HVM_PARAM_STORE_PFN is set to
+  ~0ULL (invalid) or the connection status is *not* XENSTORE_CONNECTED.
     - Old kernels will continue without xenstore support (Note: some old
       buggy kernels might crash because they don't check the validity of
       HVM_PARAM_STORE_PFN before using it! Disable "xen,enhanced" in
@@ -121,13 +122,14 @@ The implementation works as follows:
       channel (HVM_PARAM_STORE_EVTCHN) before continuing with the
       initialization
 - Once dom0 is booted, init-dom0less is executed:
-    - it allocates the xenstore shared page and sets HVM_PARAM_STORE_PFN
+    - it gets the xenstore shared page from HVM_PARAM_STORE_PFN
     - it calls xs_introduce_domain
 - Xenstored notices the new domain, initializes interfaces as usual, and
   sends an event channel notification to the domain using the xenstore
   event channel (HVM_PARAM_STORE_EVTCHN)
 - The Linux domU kernel receives the event channel notification, checks
-  HVM_PARAM_STORE_PFN again and continue with the initialization
+  HVM_PARAM_STORE_PFN and the connection status again and continue with
+  the initialization
 
 
 Limitations
-- 
2.25.1




 


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