-/* Northwestern University */
-/* (c) 2008, Jack Lange <jarusl@cs.northwestern.edu> */
+/*
+ * This file is part of the Palacios Virtual Machine Monitor developed
+ * by the V3VEE Project with funding from the United States National
+ * Science Foundation and the Department of Energy.
+ *
+ * The V3VEE Project is a joint project between Northwestern University
+ * and the University of New Mexico. You can find out more at
+ * http://www.v3vee.org
+ *
+ * Copyright (c) 2008, Jack Lange <jarusl@cs.northwestern.edu>
+ * Copyright (c) 2008, The V3VEE Project <http://www.v3vee.org>
+ * 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.enter_time = 0;
+ info->time_state.exit_time = t;
+ info->time_state.initial_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);
+ PrintDebug("Adding additional offset of %lld to guest time.\n", offset);
+ time_state->guest_cycles += 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;
+ 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;
-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));
- V3_ASSERT(timer != NULL);
+ 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;
- timer->ops = ops;
- timer->private_data = private_data;
+ return time_state->initial_time + desired_elapsed;
- list_add(&(timer->timer_link), &(info->time_state.timers));
- info->time_state.num_timers++;
+}
- return 0;
+/* 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. 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);
+ 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);
+
+ /* 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. */
+ target_guest_time = compute_target_guest_time(info);
+ guest_time = v3_get_guest_time(time_state);
+
+ if (guest_time < target_guest_time) {
+ sint64_t max_skew, desired_skew, skew;
+
+ if (time_state->enter_time) {
+ /* 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;
+ }
-int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) {
- list_del(&(timer->timer_link));
- info->time_state.num_timers--;
+ desired_skew = (sint64_t)(target_guest_time - guest_time);
+ skew = desired_skew > max_skew ? max_skew : desired_skew;
+ PrintDebug("Guest %lld cycles behind where it should be.\n",
+ desired_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;
+}
- V3_Free(timer);
- return 0;
+/* Called immediately upon entry in the the VMM */
+int
+v3_time_exit_vm( struct guest_info * info, uint64_t * guest_cycles )
+{
+ struct vm_core_time * time_state = &(info->time_state);
+
+ time_state->exit_time = v3_get_host_time(time_state);
+ if (guest_cycles) {
+ time_state->guest_cycles += *guest_cycles;
+ } else {
+ uint64_t cycles_exec;
+ cycles_exec = time_state->exit_time - time_state->enter_time;
+ time_state->guest_cycles += cycles_exec;
+ }
+ return 0;
}
+/* 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, vmm_cycles;
+
+ host_time = v3_get_host_time(time_state);
+ time_state->enter_time = host_time;
+ vmm_cycles = host_time - time_state->exit_time;
+ /* XXX How do we want to take into account host/guest CPU speed differences
+ * and time dilation here? Probably time just won't advance in the VMM in that
+ * case so its irrelvant XXX */
+ time_state->guest_cycles += vmm_cycles;
+ 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;
+ timer->private_data = private_data;
+
+ list_add(&(timer->timer_link), &(info->time_state.timers));
+ info->time_state.num_timers++;
+
+ return timer;
+}
+
+int v3_remove_timer(struct guest_info * info, struct v3_timer * timer) {
+ list_del(&(timer->timer_link));
+ info->time_state.num_timers--;
+
+ V3_Free(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 = info->time_state.last_update;
+
+ time_state->last_update = v3_get_guest_time(time_state);
+ 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
+ * 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;
+
+ /* Now do the TSC half of the instruction */
+ ret = v3_rdtsc(info);
+
+ 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 - (sint64_t)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_mult = 1;
+ PrintDebug("Setting base time dilation factor to %d.\n", vm->time_state.td_mult);
+
+ 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;
+ }
+
+ 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->tsc_guest_offset = 0;
+ time_state->enter_time = 0;
+ time_state->exit_time = 0;
+ time_state->guest_cycles = 0;
+
+ 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_update_time(struct guest_info * info, ullong_t cycles) {
- struct vm_timer * tmp_timer;
-
- info->time_state.guest_tsc += cycles;
- 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);
- }
-
+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;
}
