[v2,4/4] docs/features/dom0less: Update the late XenStore init protocol

Commit Message

Henry Wang May 11, 2024, 12:56 a.m. UTC

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

Signed-off-by: Henry Wang <[e-mail]>
---
v2:
- New patch.
---
 docs/features/dom0less.pandoc | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Patch

diff --git a/docs/features/dom0less.pandoc b/docs/features/dom0less.pandoc
index 725afa0558..137e6b618b 100644
--- a/docs/features/dom0less.pandoc
+++ b/docs/features/dom0less.pandoc
@@ -110,8 +110,9 @@  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)
+- Xen allocates the hypervisor reserved pages region (the xenstore page
+  is part of it) and sets HVM_PARAM_HV_RSRV_{BASE_PFN,SIZE} accordingly.
+  Xen sets HVM_PARAM_STORE_PFN to ~0ULL (invalid).
 - Dom0less domU kernels check that HVM_PARAM_STORE_PFN is set to invalid
     - Old kernels will continue without xenstore support (Note: some old
       buggy kernels might crash because they don't check the validity of
@@ -121,7 +122,8 @@  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_HV_RSRV_BASE_PFN
+      and sets 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