X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=51ac5a76e3a538c91506a3af39ad0cf6c76c3ab5;hb=7229981629c6baa0afb61cc99cfcf6dd029c9c93;hp=86eaa022dc25e45569cb930ca32483eb5c125fdc;hpb=266af4b5b19da7bee8e7445288c7c1cb3ee194c7;p=palacios.git

diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c
index 86eaa02..51ac5a7 100644
--- a/palacios/src/palacios/vmm_time.c
+++ b/palacios/src/palacios/vmm_time.c
@@ -12,32 +12,177 @@
  * All rights reserved.
  *
  * Author: Jack Lange <jarusl@cs.northwestern.edu>
+ *         Patrick G. Bridges <bridges@cs.unm.edu>
  *
  * This is free software.  You are permitted to use,
  * redistribute, and modify it as specified in the file "V3VEE_LICENSE".
  */
 
-#include "palacios/vmm_time.h"
-#include "palacios/vmm.h"
+#include <palacios/vmm.h>
+#include <palacios/vmm_time.h>
+#include <palacios/vm_guest.h>
 
+#ifndef V3_CONFIG_DEBUG_TIME
+#undef PrintDebug
+#define PrintDebug(fmt, args...)
+#endif
 
-void v3_init_time(struct guest_info * info) {
-    struct vm_time * time_state = &(info->time_state);
+/* Overview 
+ *
+ * Time handling in VMMs is challenging, and Palacios uses the highest 
+ * resolution, lowest overhead timer on modern CPUs that it can - the 
+ * processor timestamp counter (TSC). Note that on somewhat old processors
+ * this can be problematic; in particular, older AMD processors did not 
+ * have a constant rate timestamp counter in the face of power management
+ * events. However, the latest Intel and AMD CPUs all do (should...) have a 
+ * constant rate TSC, and Palacios relies on this fact.
+ * 
+ * Basically, Palacios keeps track of three quantities as it runs to manage
+ * 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 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.
+ *
+ * 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 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.
+ */
 
-    time_state->cpu_freq = V3_CPU_KHZ();
- 
-    time_state->guest_tsc = 0;
-    time_state->cached_host_tsc = 0;
-    // time_state->pending_cycles = 0;
-  
-    INIT_LIST_HEAD(&(time_state->timers));
-    time_state->num_timers = 0;
+
+static int handle_cpufreq_hcall(struct guest_info * info, uint_t hcall_id, void * priv_data) {
+    struct vm_core_time * time_state = &(info->time_state);
+
+    info->vm_regs.rbx = time_state->guest_cpu_freq;
+
+    PrintDebug("Guest request cpu frequency: return %ld\n", (long)info->vm_regs.rbx);
+    
+    return 0;
+}
+
+
+
+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); 
+
+    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;
+}
+
+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;
+}
+
+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;
+}
+
+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;
+
+    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 {
+	    guest_cycles = host_to_guest_cycles(info, (sint64_t)(t - info->time_state.vm_pause_host_time));
+	}
+        info->time_state.guest_cycles += guest_cycles;
+    } 
+
+    return 0;
 }
 
+int v3_advance_time(struct guest_info * info) {
+    return v3_time_advance_cycles(info, NULL);
+}
 
-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));
+/* Called immediately upon entry in the the VMM */
+int 
+v3_time_exit_vm( struct guest_info * info, uint64_t * host_cycles ) 
+{
+    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_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;
+}
+	
+
+	   
+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;
@@ -46,11 +191,10 @@ int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops, void * pri
     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--;
 
@@ -58,18 +202,241 @@ int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) {
     return 0;
 }
 
+void v3_update_timers(struct guest_info * info) {
+    struct vm_core_time *time_state = &info->time_state;
+    struct v3_timer * tmp_timer;
+    sint64_t cycles;
+    uint64_t old_time = time_state->last_update;
+
+    time_state->last_update = v3_get_guest_time(time_state);
+    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
+ * 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) {
+    uint64_t tscval = v3_get_guest_tsc(&info->time_state);
+
+    info->vm_regs.rdx = tscval >> 32;
+    info->vm_regs.rax = tscval & 0xffffffffLL;
+
+    return 0;
+}
+
+int v3_handle_rdtsc(struct guest_info * info) {
+    v3_rdtsc(info);
+    
+    info->vm_regs.rax &= 0x00000000ffffffffLL;
+    info->vm_regs.rdx &= 0x00000000ffffffffLL;
+
+    info->rip += 2;
+    
+    return 0;
+}
+
+int v3_rdtscp(struct guest_info * info) {
+    int ret;
+    /* First get the MSR value that we need. It's safe to futz with
+     * ra/c/dx here since they're modified by this instruction anyway. */
+    info->vm_regs.rcx = TSC_AUX_MSR; 
+    ret = v3_handle_msr_read(info);
+
+    if (ret != 0) {
+	return ret;
+    }
 
+    info->vm_regs.rcx = info->vm_regs.rax;
 
-void v3_update_time(struct guest_info * info, ullong_t cycles) {
-    struct vm_timer * tmp_timer;
-  
-    info->time_state.guest_tsc += cycles;
+    /* Now do the TSC half of the instruction */
+    ret = v3_rdtsc(info);
 
-    list_for_each_entry(tmp_timer, &(info->time_state.timers), timer_link) {
-	tmp_timer->ops->update_time(cycles, info->time_state.cpu_freq, tmp_timer->private_data);
+    if (ret != 0) {
+	return ret;
     }
-  
 
+    return 0;
+}
+
+
+int v3_handle_rdtscp(struct guest_info * info) {
+  PrintDebug("Handling virtual RDTSCP call.\n");
+
+    v3_rdtscp(info);
+
+    info->vm_regs.rax &= 0x00000000ffffffffLL;
+    info->vm_regs.rcx &= 0x00000000ffffffffLL;
+    info->vm_regs.rdx &= 0x00000000ffffffffLL;
+
+    info->rip += 3;
+    
+    return 0;
+}
+
+static int tsc_aux_msr_read_hook(struct guest_info *info, uint_t msr_num, 
+				 struct v3_msr *msr_val, void *priv) {
+    struct vm_core_time * time_state = &(info->time_state);
+
+    V3_ASSERT(msr_num == TSC_AUX_MSR);
+
+    msr_val->lo = time_state->tsc_aux.lo;
+    msr_val->hi = time_state->tsc_aux.hi;
+
+    return 0;
+}
+
+static int tsc_aux_msr_write_hook(struct guest_info *info, uint_t msr_num, 
+			      struct v3_msr msr_val, void *priv) {
+    struct vm_core_time * time_state = &(info->time_state);
+
+    V3_ASSERT(msr_num == TSC_AUX_MSR);
+
+    time_state->tsc_aux.lo = msr_val.lo;
+    time_state->tsc_aux.hi = msr_val.hi;
+
+    return 0;
+}
+
+static int tsc_msr_read_hook(struct guest_info *info, uint_t msr_num,
+			     struct v3_msr *msr_val, void *priv) {
+    uint64_t time = v3_get_guest_tsc(&info->time_state);
+
+    V3_ASSERT(msr_num == TSC_MSR);
+
+    msr_val->hi = time >> 32;
+    msr_val->lo = time & 0xffffffffLL;
+    
+    return 0;
+}
+
+static int tsc_msr_write_hook(struct guest_info *info, uint_t msr_num,
+			     struct v3_msr msr_val, void *priv) {
+    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 - guest_time); 
+
+    return 0;
+}
+
+
+int v3_init_time_vm(struct v3_vm_info * vm) {
+    int ret;
+
+    PrintDebug("Installing TSC MSR hook.\n");
+    ret = v3_hook_msr(vm, TSC_MSR, 
+		      tsc_msr_read_hook, tsc_msr_write_hook, NULL);
+
+    if (ret != 0) {
+	return ret;
+    }
+
+    PrintDebug("Installing TSC_AUX MSR hook.\n");
+    ret = v3_hook_msr(vm, TSC_AUX_MSR, tsc_aux_msr_read_hook, 
+		      tsc_aux_msr_write_hook, NULL);
+
+    if (ret != 0) {
+	return ret;
+    }
+
+    PrintDebug("Registering TIME_CPUFREQ hypercall.\n");
+    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;
+}
+
+void v3_deinit_time_vm(struct v3_vm_info * vm) {
+    v3_unhook_msr(vm, TSC_MSR);
+    v3_unhook_msr(vm, TSC_AUX_MSR);
+
+    v3_remove_hypercall(vm, TIME_CPUFREQ_HCALL);
+}
+
+void v3_init_time_core(struct guest_info * info) {
+    struct vm_core_time * time_state = &(info->time_state);
+    v3_cfg_tree_t * cfg_tree = info->core_cfg_data;
+    char * khz = NULL;
+
+    time_state->host_cpu_freq = V3_CPU_KHZ();
+    khz = v3_cfg_val(cfg_tree, "khz");
+
+    if (khz) {
+	time_state->guest_cpu_freq = atoi(khz);
+	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 <= 0)  || 
+	 (time_state->guest_cpu_freq > time_state->host_cpu_freq) ) {
+
+	time_state->guest_cpu_freq = time_state->host_cpu_freq;
+    }
+
+    /* 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->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;
+    
+    time_state->tsc_aux.lo = 0;
+    time_state->tsc_aux.hi = 0;
+}
+
+
+void v3_deinit_time_core(struct guest_info * core) {
+    struct vm_core_time * time_state = &(core->time_state);
+    struct v3_timer * tmr = NULL;
+    struct v3_timer * tmp = NULL;
+
+    list_for_each_entry_safe(tmr, tmp, &(time_state->timers), timer_link) {
+	v3_remove_timer(core, tmr);
+    }
 
-    //info->time_state.pending_cycles = 0;
 }