virt: Support detection for ARM64 Hyper-V guests

The detection of Microsoft Hyper-V VMs is done by cpuid currently,
however there is no cpuid on ARM64. And since ARM64 is now a supported
architecture for Microsoft Hyper-V guests[1], then use DMI tables to
detect a Hyper-V guest, which is more generic and works for ARM64.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7aff79e297ee1aa0126924921fd87a4ae59d2467

man/kernel-command-line.xml

@@ -386,8 +386,9 @@
         <term><varname>systemd.default_timeout_start_sec=</varname></term>
 
         <listitem>
-          <para>Overwrites the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at boot. For details,
-          see <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+          <para>Overrrides the default start job timeout <varname>DefaultTimeoutStartSec=</varname> at
+          boot. For details, see
+          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
         </listitem>
       </varlistentry>
 
@@ -395,7 +396,20 @@
         <term><varname>systemd.watchdog_device=</varname></term>
 
         <listitem>
-          <para>Overwrites the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
+          <para>Overrrides the watchdog device path <varname>WatchdogDevice=</varname>. For details, see
+          <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>systemd.watchdog_sec=</varname></term>
+
+        <listitem>
+          <para>Overrrides the watchdog timeout settings otherwise configured with
+          <varname>RuntimeWatchdog=</varname>, <varname>RebootWatchdog=</varname> and
+          <varname>KExecWatchdogSec=</varname>. Takes a time value (if no unit is specified, seconds is the
+          implicitly assumed time unit) or the special strings <literal>off</literal> or
+          <literal>default</literal>. For details, see
           <citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
         </listitem>
       </varlistentry>

man/systemd-system.conf.xml

@@ -135,11 +135,13 @@
 
         <listitem><para>Configure the hardware watchdog at runtime and at reboot. Takes a timeout value in
         seconds (or in other time units if suffixed with <literal>ms</literal>, <literal>min</literal>,
-        <literal>h</literal>, <literal>d</literal>, <literal>w</literal>). If set to zero the watchdog logic
-        is disabled: no watchdog device is opened, configured, or pinged. If set to the special string
-        <literal>default</literal> the watchdog is opened and pinged in regular intervals, but the timeout
-        is not changed from the default. If set to any other time value the watchdog timeout is configured to
-        the specified value (or a value close to it, depending on hardware capabilities).</para>
+        <literal>h</literal>, <literal>d</literal>, <literal>w</literal>), or the special strings
+        <literal>off</literal> or <literal>default</literal>. If set to <literal>off</literal>
+        (alternatively: <literal>0</literal>) the watchdog logic is disabled: no watchdog device is opened,
+        configured, or pinged. If set to the special string <literal>default</literal> the watchdog is opened
+        and pinged in regular intervals, but the timeout is not changed from the default. If set to any other
+        time value the watchdog timeout is configured to the specified value (or a value close to it,
+        depending on hardware capabilities).</para>
 
         <para>If <varname>RuntimeWatchdogSec=</varname> is set to a non-zero value, the watchdog hardware
         (<filename>/dev/watchdog</filename> or the path specified with <varname>WatchdogDevice=</varname> or

src/basic/virt.c

@@ -165,6 +165,7 @@ static int detect_vm_dmi_vendor(void) {
                 { "Parallels",           VIRTUALIZATION_PARALLELS },
                 /* https://wiki.freebsd.org/bhyve */
                 { "BHYVE",               VIRTUALIZATION_BHYVE     },
+                { "Microsoft",           VIRTUALIZATION_MICROSOFT },
         };
         int r;
 

src/core/load-fragment.c

@@ -6347,6 +6347,8 @@ int config_parse_watchdog_sec(
                 void *data,
                 void *userdata) {
 
+        usec_t *usec = data;
+
         assert(filename);
         assert(lvalue);
         assert(rvalue);
@@ -6354,12 +6356,12 @@ int config_parse_watchdog_sec(
         /* This is called for {Runtime,Reboot,KExec}WatchdogSec= where "default" maps to
          * USEC_INFINITY internally. */
 
-        if (streq(rvalue, "default")) {
-                usec_t *usec = data;
-
+        if (streq(rvalue, "default"))
                 *usec = USEC_INFINITY;
-                return 0;
-        }
+        else if (streq(rvalue, "off"))
+                *usec = 0;
+        else
+                return config_parse_sec(unit, filename, line, section, section_line, lvalue, ltype, rvalue, data, userdata);
 
-        return config_parse_sec(unit, filename, line, section, section_line, lvalue, ltype, rvalue, data, userdata);
+        return 0;
 }

src/core/main.c

@@ -544,6 +544,8 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
 
                 if (streq(value, "default"))
                         arg_runtime_watchdog = USEC_INFINITY;
+                else if (streq(value, "off"))
+                        arg_runtime_watchdog = 0;
                 else {
                         r = parse_sec(value, &arg_runtime_watchdog);
                         if (r < 0) {

src/core/system.conf.in

@@ -29,9 +29,9 @@
 #CPUAffinity=
 #NUMAPolicy=default
 #NUMAMask=
-#RuntimeWatchdogSec=0
+#RuntimeWatchdogSec=off
 #RebootWatchdogSec=10min
-#KExecWatchdogSec=0
+#KExecWatchdogSec=off
 #WatchdogDevice=
 #CapabilityBoundingSet=
 #NoNewPrivileges=no