#include <palacios/vmm_time.h>
#include <palacios/vm_guest.h>
-#ifndef CONFIG_DEBUG_TIME
+#ifndef V3_CONFIG_DEBUG_TIME
#undef PrintDebug
#define PrintDebug(fmt, args...)
#endif
* (1) Add support for temporarily skewing guest time off of where it should
* be to support slack simulation of guests. The idea is that simulators
* set this skew to be the difference between how much time passed for a
- * simulated feature and a real implementation of that feature, making
+ * simulated feature and a real implementation of that feature, making time
* pass at a different rate from real time on this core. The VMM will then
* attempt to move this skew back towards 0 subject to resolution/accuracy
* constraints from various system timers.
* The main effort in doing this will be to get accuracy/resolution
* information from each local timer and to use this to bound how much skew
* is removed on each exit.
+ *
+ * (2) Look more into sychronizing the offsets *across* virtual and physical
+ * cores so that multicore guests stay mostly in sync.
+ *
+ * (3) Look into using the AMD TSC multiplier feature and adding explicit time
+ * dilation support to time handling.
*/
static int handle_cpufreq_hcall(struct guest_info * info, uint_t hcall_id, void * priv_data) {
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
info->vm_regs.rbx = time_state->guest_cpu_freq;
return 0;
}
-// Control guest time in relation to host time so that the two stay
-// appropriately synchronized to the extent possible.
-int v3_adjust_time(struct guest_info * info) {
- struct vm_time * time_state = &(info->time_state);
- uint64_t host_time, target_host_time;
- uint64_t guest_time, target_guest_time, old_guest_time;
- uint64_t guest_elapsed, host_elapsed, desired_elapsed;
+int v3_pause_time( struct guest_info * info )
+{
+ struct vm_core_time * time_state = &(info->time_state);
+ if (time_state->pause_time != 0) {
+ PrintError("Attempted to pause time when time already paused.\n");
+ return -1;
+ }
+ time_state->pause_time = v3_get_host_time( time_state );
- /* Compute the target host time given how much time has *already*
- * passed in the guest */
- guest_time = v3_get_guest_time(time_state);
+ return 0;
+}
+
+int v3_resume_time( struct guest_info * info )
+{
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t host_time, guest_time;
+ sint64_t offset;
+
+ if (time_state->pause_time == 0) {
+ PrintError("Attempted to resume time when time not paused.\n");
+ return -1;
+ }
+
+ host_time = v3_get_host_time(time_state);
+ guest_time = v3_compute_guest_time(time_state, host_time);
+ offset = (sint64_t)guest_time - (sint64_t)host_time;
+ time_state->guest_host_offset = offset;
+ time_state->pause_time = 0;
+
+ return 0;
+}
+
+int v3_offset_time( struct guest_info * info, sint64_t offset )
+{
+ struct vm_core_time * time_state = &(info->time_state);
+ PrintDebug("Adding additional offset of %lld to guest time.\n", offset);
+ time_state->guest_host_offset += offset;
+ return 0;
+}
+
+#ifdef V3_CONFIG_TIME_DILATION
+static uint64_t compute_target_host_time(struct guest_info * info, uint64_t guest_time)
+{
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t guest_elapsed, desired_elapsed;
+
guest_elapsed = (guest_time - time_state->initial_time);
desired_elapsed = (guest_elapsed * time_state->host_cpu_freq) / time_state->guest_cpu_freq;
- target_host_time = time_state->initial_time + desired_elapsed;
+ return time_state->initial_time + desired_elapsed;
+}
+
+static uint64_t compute_target_guest_time(struct guest_info *info)
+{
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t host_elapsed, desired_elapsed;
+
+ host_elapsed = v3_get_host_time(time_state) - time_state->initial_time;
+ desired_elapsed = (host_elapsed * time_state->guest_cpu_freq) / time_state->host_cpu_freq;
+
+ return time_state->initial_time + desired_elapsed;
+
+}
+
+/* Yield time in the host to deal with a guest that wants to run slower than
+ * the native host cycle frequency */
+static int yield_host_time(struct guest_info * info) {
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t host_time, target_host_time;
+ uint64_t guest_time, old_guest_time;
/* Now, let the host run while the guest is stopped to make the two
- * sync up. */
+ * sync up. Note that this doesn't assume that guest time is stopped;
+ * the offsetting in the next step will change add an offset to guest
+ * time to account for the time paused even if the geust isn't
+ * usually paused in the VMM. */
host_time = v3_get_host_time(time_state);
- old_guest_time = v3_get_guest_time(time_state);
+ old_guest_time = v3_compute_guest_time(time_state, host_time);
+ target_host_time = compute_target_host_time(info, old_guest_time);
while (target_host_time > host_time) {
v3_yield(info);
host_time = v3_get_host_time(time_state);
}
- guest_time = v3_get_guest_time(time_state);
+ guest_time = v3_compute_guest_time(time_state, host_time);
- // We do *not* assume the guest timer was paused in the VM. If it was
- // this offseting is 0. If it wasn't we need this.
- v3_offset_time(info, (sint64_t)old_guest_time - (sint64_t)guest_time);
+ /* We do *not* assume the guest timer was paused in the VM. If it was
+ * this offseting is 0. If it wasn't, we need this. */
+ v3_offset_time(info, (sint64_t)(old_guest_time - guest_time));
+ return 0;
+}
+
+static int skew_guest_time(struct guest_info * info) {
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t target_guest_time, guest_time;
/* Now the host may have gotten ahead of the guest because
* yielding is a coarse grained thing. Figure out what guest time
* we want to be at, and use the use the offsetting mechanism in
* the VMM to make the guest run forward. We limit *how* much we skew
* it forward to prevent the guest time making large jumps,
* however. */
- host_elapsed = host_time - time_state->initial_time;
- desired_elapsed = (host_elapsed * time_state->guest_cpu_freq) / time_state->host_cpu_freq;
- target_guest_time = time_state->initial_time + desired_elapsed;
+ target_guest_time = compute_target_guest_time(info);
+ guest_time = v3_get_guest_time(time_state);
if (guest_time < target_guest_time) {
- uint64_t max_skew, desired_skew, skew;
+ sint64_t max_skew, desired_skew, skew;
if (time_state->enter_time) {
- max_skew = (time_state->exit_time - time_state->enter_time) / 10;
+ /* Limit forward skew to 10% of the amount the guest has
+ * run since we last could skew time */
+ max_skew = (sint64_t)(guest_time - time_state->enter_time) / 10;
} else {
max_skew = 0;
}
- desired_skew = target_guest_time - guest_time;
+ desired_skew = (sint64_t)(target_guest_time - guest_time);
skew = desired_skew > max_skew ? max_skew : desired_skew;
-/* PrintDebug("Guest %llu cycles behind where it should be.\n",
+ PrintDebug("Guest %lld cycles behind where it should be.\n",
desired_skew);
- PrintDebug("Limit on forward skew is %llu. Skewing forward %llu.\n",
- max_skew, skew); */
+ PrintDebug("Limit on forward skew is %lld. Skewing forward %lld.\n",
+ max_skew, skew);
v3_offset_time(info, skew);
}
-
+
+ return 0;
+}
+#endif /* V3_CONFIG_TIME_DILATION */
+
+// Control guest time in relation to host time so that the two stay
+// appropriately synchronized to the extent possible.
+int v3_adjust_time(struct guest_info * info) {
+
+#ifdef V3_CONFIG_TIME_DILATION
+ /* First deal with yielding if we want to slow down the guest */
+ yield_host_time(info);
+
+ /* Now, if the guest is too slow, (either from excess yielding above,
+ * or because the VMM is doing something that takes a long time to emulate)
+ * allow guest time to jump forward a bit */
+ skew_guest_time(info);
+#endif
return 0;
}
/* Called immediately upon entry in the the VMM */
int
-v3_time_exit_vm( struct guest_info * info )
+v3_time_exit_vm( struct guest_info * info, uint64_t * guest_cycles )
{
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
time_state->exit_time = v3_get_host_time(time_state);
+#ifdef V3_CONFIG_TIME_DILATION
+ v3_pause_time( info );
+#endif
+
return 0;
}
int
v3_time_enter_vm( struct guest_info * info )
{
- struct vm_time * time_state = &(info->time_state);
- uint64_t guest_time, host_time;
+ struct vm_core_time * time_state = &(info->time_state);
+ uint64_t host_time;
- guest_time = v3_get_guest_time(time_state);
host_time = v3_get_host_time(time_state);
time_state->enter_time = host_time;
- time_state->guest_host_offset = guest_time - host_time;
-
- // Because we just modified the offset - shouldn't matter as this should be
- // the last time-related call prior to entering the VMM, but worth it
- // just in case.
- time_state->exit_time = host_time;
+#ifdef V3_CONFIG_TIME_DILATION
+ v3_resume_time( info );
+#else
+ time_state->guest_host_offset = 0;
+#endif
return 0;
}
-int v3_offset_time( struct guest_info * info, sint64_t offset )
-{
- struct vm_time * time_state = &(info->time_state);
-// PrintDebug("Adding additional offset of %lld to guest time.\n", offset);
- time_state->guest_host_offset += offset;
- return 0;
-}
+
struct v3_timer * v3_add_timer(struct guest_info * info,
struct v3_timer_ops * ops,
}
void v3_update_timers(struct guest_info * info) {
- struct vm_time *time_state = &info->time_state;
+ struct vm_core_time *time_state = &info->time_state;
struct v3_timer * tmp_timer;
- uint64_t old_time = info->time_state.last_update;
sint64_t cycles;
+ uint64_t old_time = info->time_state.last_update;
time_state->last_update = v3_get_guest_time(time_state);
- cycles = time_state->last_update - old_time;
+ cycles = (sint64_t)(time_state->last_update - old_time);
+ V3_ASSERT(cycles >= 0);
+ // V3_Print("Updating timers with %lld elapsed cycles.\n", cycles);
list_for_each_entry(tmp_timer, &(time_state->timers), timer_link) {
tmp_timer->ops->update_timer(info, cycles, time_state->guest_cpu_freq, tmp_timer->private_data);
}
}
+
/*
* Handle full virtualization of the time stamp counter. As noted
* above, we don't store the actual value of the TSC, only the guest's
static int tsc_aux_msr_read_hook(struct guest_info *info, uint_t msr_num,
struct v3_msr *msr_val, void *priv) {
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
V3_ASSERT(msr_num == TSC_AUX_MSR);
static int tsc_aux_msr_write_hook(struct guest_info *info, uint_t msr_num,
struct v3_msr msr_val, void *priv) {
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
V3_ASSERT(msr_num == TSC_AUX_MSR);
static int tsc_msr_write_hook(struct guest_info *info, uint_t msr_num,
struct v3_msr msr_val, void *priv) {
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
uint64_t guest_time, new_tsc;
V3_ASSERT(msr_num == TSC_MSR);
ret = v3_register_hypercall(vm, TIME_CPUFREQ_HCALL,
handle_cpufreq_hcall, NULL);
+ PrintDebug("Setting base time dilation factor.\n");
+ vm->time_state.td_mult = 1;
+
return ret;
}
}
void v3_init_time_core(struct guest_info * info) {
- struct vm_time * time_state = &(info->time_state);
+ struct vm_core_time * time_state = &(info->time_state);
v3_cfg_tree_t * cfg_tree = info->core_cfg_data;
char * khz = NULL;
if (khz) {
time_state->guest_cpu_freq = atoi(khz);
- PrintDebug("Core %d CPU frequency requested at %d khz.\n",
- info->cpu_id, time_state->guest_cpu_freq);
+ PrintDebug("Logical Core %d (vcpu=%d) CPU frequency requested at %d khz.\n",
+ info->pcpu_id, info->vcpu_id, time_state->guest_cpu_freq);
}
if ( (khz == NULL) ||
time_state->guest_cpu_freq = time_state->host_cpu_freq;
}
- PrintDebug("Core %d CPU frequency set to %d KHz (host CPU frequency = %d KHz).\n",
- info->cpu_id,
+ PrintDebug("Logical Core %d (vcpu=%d) CPU frequency set to %d KHz (host CPU frequency = %d KHz).\n",
+ info->pcpu_id, info->vcpu_id,
time_state->guest_cpu_freq,
time_state->host_cpu_freq);
time_state->last_update = 0;
time_state->guest_host_offset = 0;
time_state->tsc_guest_offset = 0;
+ time_state->enter_time = 0;
+ time_state->exit_time = 0;
+ time_state->pause_time = 0;
+
INIT_LIST_HEAD(&(time_state->timers));
time_state->num_timers = 0;
void v3_deinit_time_core(struct guest_info * core) {
- struct vm_time * time_state = &(core->time_state);
+ struct vm_core_time * time_state = &(core->time_state);
struct v3_timer * tmr = NULL;
struct v3_timer * tmp = NULL;
