X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=51ac5a76e3a538c91506a3af39ad0cf6c76c3ab5;hb=dd60e1fd40cdf258bd988239c5dcda8861a5bbb5;hp=2880f5d39974c09940985e126f20736d18679d39;hpb=305267e8eaabf7dffadd86abc323f7d1b231e388;p=palacios.git

diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c
index 2880f5d..51ac5a7 100644
--- a/palacios/src/palacios/vmm_time.c
+++ b/palacios/src/palacios/vmm_time.c
@@ -22,7 +22,7 @@
 #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
@@ -41,15 +41,14 @@
  * 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 using an offsets from (1) above.
+ *     time in the guest. This is stored as an absolute number of cycles elapsed
+ *     and is updated on guest entry and exit; it can also be updated explicitly
+ *     in the monitor at times
  * (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).
@@ -58,7 +57,7 @@
  * (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.
@@ -66,11 +65,17 @@
  *     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;
 
@@ -85,118 +90,93 @@ int v3_start_time(struct guest_info * info) {
     /* We start running with guest_time == host_time */
     uint64_t t = v3_get_host_time(&info->time_state); 
 
-    PrintDebug("Starting initial guest time as %llu\n", t);
-
-    info->time_state.enter_time = 0;
-    info->time_state.exit_time = t; 
-    info->time_state.last_update = t;
-    info->time_state.initial_time = t;
+    info->time_state.vm_enter_host_time = 0;
+    info->time_state.vm_pause_host_time = t; 
+    info->time_state.initial_host_time = t;
     info->yield_start_cycle = t;
 
+    info->time_state.last_update = 0;
+    info->time_state.guest_cycles = 0;
+    PrintDebug("Starting time for core %d at host time %llu/guest time %llu.\n",
+	       info->vcpu_id, t, info->time_state.guest_cycles); 
+    v3_yield(info);
     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_offset_time( struct guest_info * info, sint64_t offset )
+{
+    struct vm_core_time * time_state = &(info->time_state);
+    if (info->vm_info->time_state.follow_host_time) {
+	PrintError("Cannot offset guest time passage while slaved to host clock.\n");
+	return 1;
+    } else {
+        time_state->guest_cycles += offset;
+    }
+    return 0;
+}
 
-    /* Compute the target host time given how much time has *already*
-     * passed in the guest */
-    guest_time = v3_get_guest_time(time_state);
-    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;
-
-    /* Now, let the host run while the guest is stopped to make the two
-     * sync up. */
-    host_time = v3_get_host_time(time_state);
-    old_guest_time = v3_get_guest_time(time_state);
-
-    while (target_host_time > host_time) {
-	v3_yield(info);
-	host_time = v3_get_host_time(time_state);
+int v3_skip_time(struct guest_info * info) {
+    if (info->vm_info->time_state.follow_host_time) {
+	PrintError("Cannot skip guest time passage while slaved to host clock.\n");
+	return 1;
+    } else {
+        info->time_state.vm_pause_host_time = v3_get_host_time(&info->time_state);
     }
+    return 0;
+}
 
-    guest_time = v3_get_guest_time(time_state);
+static sint64_t host_to_guest_cycles(struct guest_info * info, sint64_t host_cycles) {
+    return (host_cycles * info->time_state.clock_ratio_num) / info->time_state.clock_ratio_denom;
+}
+
+int v3_time_advance_cycles(struct guest_info * info, uint64_t *host_cycles)
+{
+    uint64_t t = v3_get_host_time(&info->time_state);
+
+    info->time_state.vm_pause_host_time = t;
 
-    // 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);
-
-    /* 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;
-
-    if (guest_time < target_guest_time) {
-	uint64_t max_skew, desired_skew, skew;
-
-	if (time_state->enter_time) {
-	    max_skew = (time_state->exit_time - time_state->enter_time) / 10;
+    if (info->vm_info->time_state.follow_host_time) {
+	/* How many guest cycles should have elapsed? */
+	sint64_t host_elapsed = t - info->time_state.initial_host_time;
+	sint64_t guest_elapsed = host_to_guest_cycles(info, host_elapsed);
+
+	info->time_state.guest_cycles = guest_elapsed;
+    } else {
+        uint64_t guest_cycles;
+	if (*host_cycles) {
+	    guest_cycles = host_to_guest_cycles(info, *host_cycles);
 	} else {
-	    max_skew = 0;
+	    guest_cycles = host_to_guest_cycles(info, (sint64_t)(t - info->time_state.vm_pause_host_time));
 	}
+        info->time_state.guest_cycles += guest_cycles;
+    } 
 
-	desired_skew = target_guest_time - guest_time;
-	skew = desired_skew > max_skew ? max_skew : desired_skew;
-/*	PrintDebug("Guest %llu cycles behind where it should be.\n",
-		   desired_skew);
-	PrintDebug("Limit on forward skew is %llu. Skewing forward %llu.\n",
-	           max_skew, skew); */
-	
-	v3_offset_time(info, skew);
-    }
-    
     return 0;
 }
 
+int v3_advance_time(struct guest_info * info) {
+    return v3_time_advance_cycles(info, NULL);
+}
+
 /* 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 * host_cycles ) 
 {
-    struct vm_time * time_state = &(info->time_state);
-    
-    time_state->exit_time = v3_get_host_time(time_state);
-
-    return 0;
+    return v3_time_advance_cycles(info, host_cycles);
 }
 
 /* Called immediately prior to entry to the VM */
 int 
 v3_time_enter_vm( struct guest_info * info )
 {
-    struct vm_time * time_state = &(info->time_state);
-    uint64_t guest_time, 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; 
+    struct vm_core_time * time_state = &(info->time_state);
+    uint64_t host_time = v3_get_host_time(&info->time_state);
 
+    time_state->vm_enter_host_time = host_time;
     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, 
@@ -223,19 +203,26 @@ int v3_remove_timer(struct guest_info * info, struct v3_timer * timer) {
 }
 
 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 = 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);
+    if (cycles < 0) {
+	PrintError("Cycles appears to have rolled over - old time %lld, current time %lld.\n",
+		   old_time, time_state->last_update);
+	return;
+    }
 
+    PrintDebug("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
@@ -305,7 +292,7 @@ int v3_handle_rdtscp(struct guest_info * info) {
 
 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);
 
@@ -317,7 +304,7 @@ static int tsc_aux_msr_read_hook(struct guest_info *info, uint_t msr_num,
 
 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);
 
@@ -341,14 +328,14 @@ static int tsc_msr_read_hook(struct guest_info *info, uint_t msr_num,
 
 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);
 
     new_tsc = (((uint64_t)msr_val.hi) << 32) | (uint64_t)msr_val.lo;
     guest_time = v3_get_guest_time(time_state);
-    time_state->tsc_guest_offset = (sint64_t)new_tsc - (sint64_t)guest_time; 
+    time_state->tsc_guest_offset = (sint64_t)(new_tsc - guest_time); 
 
     return 0;
 }
@@ -377,6 +364,13 @@ int v3_init_time_vm(struct v3_vm_info * vm) {
     ret = v3_register_hypercall(vm, TIME_CPUFREQ_HCALL, 
 				handle_cpufreq_hcall, NULL);
 
+    vm->time_state.td_num = 1;
+    vm->time_state.td_denom = 1;
+    PrintDebug("Setting base time dilation factor to %d/%d.\n", 
+	       vm->time_state.td_num, vm->time_state.td_denom);
+
+    vm->time_state.follow_host_time = 1;
+    PrintDebug("Locking guest time to host time.\n");
     return ret;
 }
 
@@ -388,7 +382,7 @@ void v3_deinit_time_vm(struct v3_vm_info * vm) {
 }
 
 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;
 
@@ -397,8 +391,8 @@ void v3_init_time_core(struct guest_info * info) {
 
     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) || 
@@ -408,15 +402,25 @@ void v3_init_time_core(struct guest_info * info) {
 	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, 
+    /* Compute these using the GCD() of the guest and host CPU freq.
+     * If the GCD is too small, make it "big enough" */
+    time_state->clock_ratio_num = 1;
+    time_state->clock_ratio_denom = 1;
+
+    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->initial_time = 0;
-    time_state->last_update = 0;
-    time_state->guest_host_offset = 0;
+    time_state->guest_cycles = 0;
     time_state->tsc_guest_offset = 0;
+    time_state->last_update = 0;
+
+    time_state->initial_host_time = 0;
+    time_state->vm_enter_host_time = 0;
+    time_state->vm_pause_host_time = 0;
+
+    time_state->time_flags = 0; // XXX need to set trap TSC flag or not wisely
 
     INIT_LIST_HEAD(&(time_state->timers));
     time_state->num_timers = 0;
@@ -427,7 +431,7 @@ void v3_init_time_core(struct guest_info * info) {
 
 
 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;