1 files changed, 124 insertions, 7 deletions

diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 0c572a48158e..6a051b078359 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -19,11 +19,29 @@
 #include <kern_util.h>
 #include <os.h>
 #include <timer-internal.h>
+#include <shared/init.h>
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+enum time_travel_mode time_travel_mode;
+unsigned long long time_travel_time;
+enum time_travel_timer_mode time_travel_timer_mode;
+unsigned long long time_travel_timer_expiry;
+unsigned long long time_travel_timer_interval;
+
+static bool time_travel_start_set;
+static unsigned long long time_travel_start;
+#else
+#define time_travel_start_set 0
+#define time_travel_start 0
+#endif
 
 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
         unsigned long flags;
 
+        if (time_travel_mode != TT_MODE_OFF)
+                time_travel_set_time(time_travel_timer_expiry);
+
         local_irq_save(flags);
         do_IRQ(TIMER_IRQ, regs);
         local_irq_restore(flags);
@@ -31,26 +49,47 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 
 static int itimer_shutdown(struct clock_event_device *evt)
 {
-        os_timer_disable();
+        if (time_travel_mode != TT_MODE_OFF)
+                time_travel_set_timer(TT_TMR_DISABLED, 0);
+
+        if (time_travel_mode != TT_MODE_INFCPU)
+                os_timer_disable();
+
         return 0;
 }
 
 static int itimer_set_periodic(struct clock_event_device *evt)
 {
-        os_timer_set_interval(NULL, NULL);
+        unsigned long long interval = NSEC_PER_SEC / HZ;
+
+        if (time_travel_mode != TT_MODE_OFF)
+                time_travel_set_timer(TT_TMR_PERIODIC,
+                                      time_travel_time + interval);
+
+        if (time_travel_mode != TT_MODE_INFCPU)
+                os_timer_set_interval(interval);
+
         return 0;
 }
 
 static int itimer_next_event(unsigned long delta,
                              struct clock_event_device *evt)
 {
-        return os_timer_one_shot(delta);
+        delta += 1;
+
+        if (time_travel_mode != TT_MODE_OFF)
+                time_travel_set_timer(TT_TMR_ONESHOT,
+                                      time_travel_time + delta);
+
+        if (time_travel_mode != TT_MODE_INFCPU)
+                return os_timer_one_shot(delta);
+
+        return 0;
 }
 
 static int itimer_one_shot(struct clock_event_device *evt)
 {
-        os_timer_one_shot(1);
-        return 0;
+        return itimer_next_event(0, evt);
 }
 
 static struct clock_event_device timer_clockevent = {
@@ -87,6 +126,17 @@ static irqreturn_t um_timer(int irq, void *dev)
 
 static u64 timer_read(struct clocksource *cs)
 {
+        if (time_travel_mode != TT_MODE_OFF) {
+                /*
+                 * We make reading the timer cost a bit so that we don't get
+                 * stuck in loops that expect time to move more than the
+                 * exact requested sleep amount, e.g. python's socket server,
+                 * see https://bugs.python.org/issue37026.
+                 */
+                time_travel_set_time(time_travel_time + TIMER_MULTIPLIER);
+                return time_travel_time / TIMER_MULTIPLIER;
+        }
+
         return os_nsecs() / TIMER_MULTIPLIER;
 }
 
@@ -107,7 +157,7 @@ static void __init um_timer_setup(void)
                 printk(KERN_ERR "register_timer : request_irq failed - "
                        "errno = %d\n", -err);
 
-        err = os_timer_create(NULL);
+        err = os_timer_create();
         if (err != 0) {
                 printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
                 return;
@@ -123,7 +173,12 @@ static void __init um_timer_setup(void)
 
 void read_persistent_clock64(struct timespec64 *ts)
 {
-        long long nsecs = os_persistent_clock_emulation();
+        long long nsecs;
+
+        if (time_travel_start_set)
+                nsecs = time_travel_start + time_travel_time;
+        else
+                nsecs = os_persistent_clock_emulation();
 
         set_normalized_timespec64(ts, nsecs / NSEC_PER_SEC,
                                   nsecs % NSEC_PER_SEC);
@@ -134,3 +189,65 @@ void __init time_init(void)
         timer_set_signal_handler();
         late_time_init = um_timer_setup;
 }
+
+#ifdef CONFIG_UML_TIME_TRAVEL_SUPPORT
+unsigned long calibrate_delay_is_known(void)
+{
+        if (time_travel_mode == TT_MODE_INFCPU)
+                return 1;
+        return 0;
+}
+
+int setup_time_travel(char *str)
+{
+        if (strcmp(str, "=inf-cpu") == 0) {
+                time_travel_mode = TT_MODE_INFCPU;
+                timer_clockevent.name = "time-travel-timer-infcpu";
+                timer_clocksource.name = "time-travel-clock";
+                return 1;
+        }
+
+        if (!*str) {
+                time_travel_mode = TT_MODE_BASIC;
+                timer_clockevent.name = "time-travel-timer";
+                timer_clocksource.name = "time-travel-clock";
+                return 1;
+        }
+
+        return -EINVAL;
+}
+
+__setup("time-travel", setup_time_travel);
+__uml_help(setup_time_travel,
+"time-travel\n"
+"This option just enables basic time travel mode, in which the clock/timers\n"
+"inside the UML instance skip forward when there's nothing to do, rather than\n"
+"waiting for real time to elapse. However, instance CPU speed is limited by\n"
+"the real CPU speed, so e.g. a 10ms timer will always fire after ~10ms wall\n"
+"clock (but quicker when there's nothing to do).\n"
+"\n"
+"time-travel=inf-cpu\n"
+"This enables time travel mode with infinite processing power, in which there\n"
+"are no wall clock timers, and any CPU processing happens - as seen from the\n"
+"guest - instantly. This can be useful for accurate simulation regardless of\n"
+"debug overhead, physical CPU speed, etc. but is somewhat dangerous as it can\n"
+"easily lead to getting stuck (e.g. if anything in the system busy loops).\n");
+
+int setup_time_travel_start(char *str)
+{
+        int err;
+
+        err = kstrtoull(str, 0, &time_travel_start);
+        if (err)
+                return err;
+
+        time_travel_start_set = 1;
+        return 1;
+}
+
+__setup("time-travel-start", setup_time_travel_start);
+__uml_help(setup_time_travel_start,
+"time-travel-start=<seconds>\n"
+"Configure the UML instance's wall clock to start at this value rather than\n"
+"the host's wall clock at the time of UML boot.\n");
+#endif