9004-machine-id-setup-generate-stable-ID-under-Xen.patch

From a659db335da0bf8e27c851fe3f8ae30c7c0f5eaf Mon Sep 17 00:00:00 2001
From: Ben Cressey <bcressey@amazon.com>
Date: Tue, 7 Jul 2020 22:38:20 +0000
Subject: [PATCH 9004/9006] machine-id-setup: generate stable ID under Xen

Signed-off-by: Ben Cressey <bcressey@amazon.com>
---
 man/machine-id.xml          |  3 ++-
 src/core/machine-id-setup.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/man/machine-id.xml b/man/machine-id.xml
index bd55366..6a58b9d 100644
--- a/man/machine-id.xml
+++ b/man/machine-id.xml
@@ -100,7 +100,8 @@
     to use the D-Bus machine ID from <filename>/var/lib/dbus/machine-id</filename>, the
     value of the kernel command line option <varname>container_uuid</varname>, the KVM DMI
     <filename>product_uuid</filename> or the devicetree <filename>vm,uuid</filename>
-    (on KVM systems), and finally a randomly generated UUID.</para>
+    (on KVM systems), the hypervisor UUID from <filename>/sys/hypervisor/uuid</filename>
+    (under Xen), and finally a randomly generated UUID.</para>
 
     <para>After the machine ID is established,
     <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
diff --git a/src/core/machine-id-setup.c b/src/core/machine-id-setup.c
index f76b82a..d2024ee 100644
--- a/src/core/machine-id-setup.c
+++ b/src/core/machine-id-setup.c
@@ -73,6 +73,16 @@ static int generate_machine_id(const char *root, sd_id128_t *ret) {
                                 log_info("Initializing machine ID from KVM UUID.");
                                 return 0;
                         }
+
+                } else if (detect_vm() == VIRTUALIZATION_XEN) {
+
+                        /* Otherwise, if we're running under Xen, check for
+                         * a UUID from the hypervisor. */
+
+                        if (id128_read("/sys/hypervisor/uuid", ID128_UUID, ret) >= 0) {
+                                log_info("Initializing machine ID from Xen UUID.");
+                                return 0;
+                        }
                 }
         }
 
-- 
2.26.2