Allow setting the used wallclock from the command line. When the option is set
to a value different than `auto` the probing is bypassed and the selected
implementation is used (as long as it's available).
The `xen` and `efi` options require being booted as a Xen guest (with Xen guest
supported built-in) or from UEFI firmware.
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
docs/misc/xen-command-line.pandoc | 18 +++++++++++++++++
xen/arch/x86/time.c | 33 ++++++++++++++++++++++++++++++-
2 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 0a66e1ee2d7e..23de922b9705 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -2821,6 +2821,24 @@ vwfi to `native` reduces irq latency significantly. It can also lead to
suboptimal scheduling decisions, but only when the system is
oversubscribed (i.e., in total there are more vCPUs than pCPUs).
+### wallclock (x86)
+> `= auto | xen | cmos | efi`
+
+> Default: `auto`
+
+Allow forcing the usage of a specific wallclock source.
+
+ * `auto` let the hypervisor select the clocksource based on internal
+ heuristics.
+
+ * `xen` force usage of the Xen shared_info wallclock when booted as a Xen
+ guest.
+
+ * `cmos` force usage of the CMOS RTC wallclock.
+
+ * `efi` force usage of the EFI_GFET_TIME run-time method when booted from EFI
+ firmware.
+
### watchdog (x86)
> `= force | <boolean>`
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index da3fd1555041..6e19c666d13f 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1555,6 +1555,36 @@ static const char *wallclock_type_to_string(void)
return "";
}
+static int __init cf_check parse_wallclock(const char *arg)
+{
+ if ( !arg )
+ return -EINVAL;
+
+ if ( !strcmp("auto", arg) )
+ wallclock_source = WALLCLOCK_UNSET;
+ else if ( !strcmp("xen", arg) )
+ {
+ if ( !xen_guest )
+ return -EINVAL;
+
+ wallclock_source = WALLCLOCK_XEN;
+ }
+ else if ( !strcmp("cmos", arg) )
+ wallclock_source = WALLCLOCK_CMOS;
+ else if ( !strcmp("efi", arg) )
+ {
+ if ( !efi_enabled(EFI_RS) )
+ return -EINVAL;
+
+ wallclock_source = WALLCLOCK_EFI;
+ }
+ else
+ return -EINVAL;
+
+ return 0;
+}
+custom_param("wallclock", parse_wallclock);
+
static void __init probe_wallclock(void)
{
ASSERT(wallclock_source == WALLCLOCK_UNSET);
@@ -2527,7 +2557,8 @@ int __init init_xen_time(void)
open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration);
- probe_wallclock();
+ if ( wallclock_source == WALLCLOCK_UNSET )
+ probe_wallclock();
printk(XENLOG_INFO "Wallclock source: %s\n", wallclock_type_to_string());
--
2.46.0