X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=48a15796bcdae939e778ed6c956ad6e03b30dfcc;hb=d962f2be029772be3f21d9bd206ddf2a9f6a1d20;hp=e191e9ff6672151be09c12531322eeb99396554f;hpb=2869a01dc962b40e05da69dd7eb628ac1dd41af7;p=palacios.git

diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c
index e191e9f..48a1579 100644
--- a/palacios/src/palacios/vmm_time.c
+++ b/palacios/src/palacios/vmm_time.c
@@ -41,18 +41,31 @@
  * the passage of time:
  * (1) The host timestamp counter - read directly from HW and never written
  * (2) A monotonic guest timestamp counter used to measure the progression of
- *     time in the guest. This is computed as a multipler/offset from (1) above
+ *     time in the guest. This is computed using an offsets from (1) above.
  * (3) The actual guest timestamp counter (which can be written by
  *     writing to the guest TSC MSR - MSR 0x10) from the monotonic guest TSC.
  *     This is also computed as an offset from (2) above when the TSC and
  *     this offset is updated when the TSC MSR is written.
  *
+ * The value used to offset the guest TSC from the host TSC is the *sum* of all
+ * of these offsets (2 and 3) above
+ * 
  * Because all other devices are slaved off of the passage of time in the guest,
  * it is (2) above that drives the firing of other timers in the guest, 
  * including timer devices such as the Programmable Interrupt Timer (PIT).
  *
- *  
- *
+ * Future additions:
+ * (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 
+ *     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.
  */
 
 
@@ -83,28 +96,37 @@ int v3_start_time(struct guest_info * info) {
 // the host time is appropriately far along;
 int v3_adjust_time(struct guest_info * info) {
     struct vm_time * time_state = &(info->time_state);
+
     if (time_state->host_cpu_freq == time_state->guest_cpu_freq) {
 	time_state->guest_host_offset = 0;
     } else {
-	uint64_t guest_time, host_time, target_host_time;
+	uint64_t guest_time, guest_elapsed, desired_elapsed;
+	uint64_t host_time, target_host_time;
+
 	guest_time = v3_get_guest_time(time_state);
+
+	/* Compute what host time this guest time should correspond to. */
+	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;
+
+	/* Yield until that host time is reached */
 	host_time = v3_get_host_time(time_state);
-	target_host_time = (host_time - time_state->initial_time) *
-	    time_state->host_cpu_freq / time_state->guest_cpu_freq;
 	while (host_time < target_host_time) {
 	    v3_yield(info);
 	    host_time = v3_get_host_time(time_state);
 	}
-	time_state->guest_host_offset = guest_time - host_time;
 
+	time_state->guest_host_offset = (sint64_t)guest_time - (sint64_t)host_time;
     }
     return 0;
 }
 
-int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops, 
-	     void * private_data) {
-    struct vm_timer * timer = NULL;
-    timer = (struct vm_timer *)V3_Malloc(sizeof(struct vm_timer));
+struct v3_timer * v3_add_timer(struct guest_info * info, 
+			       struct v3_timer_ops * ops, 
+			       void * private_data) {
+    struct v3_timer * timer = NULL;
+    timer = (struct v3_timer *)V3_Malloc(sizeof(struct v3_timer));
     V3_ASSERT(timer != NULL);
 
     timer->ops = ops;
@@ -113,10 +135,10 @@ int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops,
     list_add(&(timer->timer_link), &(info->time_state.timers));
     info->time_state.num_timers++;
 
-    return 0;
+    return timer;
 }
 
-int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) {
+int v3_remove_timer(struct guest_info * info, struct v3_timer * timer) {
     list_del(&(timer->timer_link));
     info->time_state.num_timers--;
 
@@ -125,7 +147,7 @@ int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) {
 }
 
 void v3_update_timers(struct guest_info * info) {
-    struct vm_timer * tmp_timer;
+    struct v3_timer * tmp_timer;
     uint64_t old_time = info->time_state.last_update;
     uint64_t cycles;
 
@@ -140,8 +162,10 @@ void v3_update_timers(struct guest_info * info) {
 /* 
  * 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
- * offset from the host TSC. If the guest write's the to TSC, we handle
- * this by changing that offset.
+ * offset from monotonic guest's time. If the guest writes to the TSC, we
+ * handle this by changing that offset.
+ *
+ * Possible TODO: Proper hooking of TSC read/writes?
  */ 
 
 int v3_rdtsc(struct guest_info * info) {
@@ -171,8 +195,7 @@ int v3_rdtscp(struct guest_info * info) {
     if (ret) return ret;
     info->vm_regs.rcx = info->vm_regs.rax;
 
-    /* Now do the TSC half of the instruction, which may hit the normal 
-     * TSC hook if it exists */
+    /* Now do the TSC half of the instruction */
     ret = v3_rdtsc(info);
     if (ret) return ret;
     
@@ -238,6 +261,7 @@ static int tsc_msr_write_hook(struct guest_info *info, uint_t msr_num,
     return 0;
 }
 
+
 static int init_vm_time(struct v3_vm_info *vm_info) {
     int ret;
 
@@ -259,11 +283,23 @@ static int init_vm_time(struct v3_vm_info *vm_info) {
 
 void v3_init_time(struct guest_info * info) {
     struct vm_time * time_state = &(info->time_state);
+    v3_cfg_tree_t * cfg_tree = info->core_cfg_data;
     static int one_time = 0;
+    char *khz;
 
     time_state->host_cpu_freq = V3_CPU_KHZ();
-    time_state->guest_cpu_freq = V3_CPU_KHZ();
- 
+    khz = v3_cfg_val(cfg_tree, "khz");
+    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);
+    }
+    
+    if (!khz || time_state->guest_cpu_freq > time_state->host_cpu_freq) {
+	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, time_state->guest_cpu_freq, time_state->host_cpu_freq);
+
     time_state->initial_time = 0;
     time_state->last_update = 0;
     time_state->guest_host_offset = 0;
@@ -286,3 +322,6 @@ void v3_init_time(struct guest_info * info) {
 
 
 
+
+
+