/* * 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 * Copyright (c) 2008, The V3VEE Project * All rights reserved. * * Author: Jack Lange * Patrick G. Bridges * * This is free software. You are permitted to use, * redistribute, and modify it as specified in the file "V3VEE_LICENSE". */ #include #include #include #ifndef V3_CONFIG_DEBUG_TIME #undef PrintDebug #define PrintDebug(fmt, args...) #endif /* 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. */ 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(info->vm_info, info, "Guest request cpu frequency: return %ld\n", (long)info->vm_regs.rbx); return 0; } static int handle_rdhtsc_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 = v3_get_host_time(time_state); // PrintDebug(info->vm_info, info, "Guest request host TSC: 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.initial_host_time = t; info->yield_start_cycle = t; info->time_state.last_update = 0; info->time_state.guest_cycles = 0; PrintDebug(info->vm_info, info, "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,-1); return 0; } static sint64_t host_to_guest_cycles(struct guest_info * info, sint64_t host_cycles) { struct vm_core_time * core_time_state = &(info->time_state); uint32_t cl_num, cl_denom; cl_num = core_time_state->clock_ratio_num; cl_denom = core_time_state->clock_ratio_denom; return (host_cycles * cl_num) / cl_denom; } /* static sint64_t guest_to_host_cycles(struct guest_info * info, sint64_t guest_cycles) { struct vm_core_time * core_time_state = &(info->time_state); uint32_t cl_num, cl_denom; cl_num = core_time_state->clock_ratio_num; cl_denom = core_time_state->clock_ratio_denom; return (guest_cycles * cl_denom) / cl_num; } */ int v3_advance_time(struct guest_info * info, uint64_t *host_cycles) { uint64_t guest_cycles; if (info->time_state.flags & VM_TIME_SLAVE_HOST) { struct v3_time *vm_ts = &(info->vm_info->time_state); uint64_t ht = v3_get_host_time(&info->time_state); uint64_t host_elapsed = ht - info->time_state.initial_host_time; uint64_t dilated_elapsed = (host_elapsed * vm_ts->td_num) / vm_ts->td_denom; uint64_t guest_elapsed = host_to_guest_cycles(info, dilated_elapsed); guest_cycles = guest_elapsed - v3_get_guest_time(&info->time_state); } else if (host_cycles) { guest_cycles = host_to_guest_cycles(info, *host_cycles); } else { guest_cycles = 0; } info->time_state.guest_cycles += guest_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)); if (!timer) { PrintError(info->vm_info, info, "Cannot allocate in adding a timer\n"); return NULL; } V3_ASSERT(info->vm_info, info,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 = 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(info->vm_info, info, "Cycles appears to have rolled over - old time %lld, current time %lld.\n", old_time, time_state->last_update); return; } //PrintDebug(info->vm_info, info, "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) { PrintDebug(info->vm_info, info, "Handling virtual RDTSC call.\n"); 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(info->vm_info, info, "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(info->vm_info, info,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(info->vm_info, info,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); PrintDebug(info->vm_info, info, "Handling virtual TSC MSR read call.\n"); V3_ASSERT(info->vm_info, info,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; PrintDebug(info->vm_info, info, "Handling virtual TSC MSR write call.\n"); V3_ASSERT(info->vm_info, info,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; } static int handle_time_configuration(struct v3_vm_info * vm, v3_cfg_tree_t *cfg) { char *source, *dilation, *tsc; vm->time_state.flags = V3_TIME_SLAVE_HOST; vm->time_state.td_num = vm->time_state.td_denom = 1; if (!cfg) return 0; source = v3_cfg_val(cfg, "source"); if (source) { if (strcasecmp(source, "none") == 0) { vm->time_state.flags &= ~V3_TIME_SLAVE_HOST; } else if (strcasecmp(source, "host") != 0) { PrintError(vm, VCORE_NONE, "Unknown time source for VM core time management.\n"); } else { PrintDebug(vm, VCORE_NONE,"VM time slaved to host TSC.\n"); } } // Should we make a separate TSC device that handles this sort of thing? tsc = v3_cfg_val(cfg, "tsc"); if (tsc) { if (strcasecmp(tsc, "host") == 0) { if (!(vm->time_state.flags & V3_TIME_SLAVE_HOST)) { PrintError(vm, VCORE_NONE, "WARNING: Guest TSC set to passthrough host TSC, but guest time not slaved to host time."); } vm->time_state.flags |= V3_TIME_TSC_PASSTHROUGH; } else if (!source || (strcasecmp(source, "guest") != 0)) { PrintError(vm, VCORE_NONE, "ERROR: Unknown TSC configuration in time configuration.\n"); } } dilation = v3_cfg_val(cfg, "dilation"); if (dilation) { if (!(vm->time_state.flags & VM_TIME_SLAVE_HOST)) { PrintError(vm, VCORE_NONE, "Time dilation only valid when slaved to host time.\n"); } else { uint32_t num = 1, denom = 1; denom = atoi(dilation); if ((num > 0) && (denom > 0)) { vm->time_state.td_num = num; vm->time_state.td_denom = denom; } } if ((vm->time_state.td_num != 1) || (vm->time_state.td_denom != 1)) { V3_Print(vm, VCORE_NONE, "Time dilated from host time by a factor of %d/%d" " in guest.\n", vm->time_state.td_denom, vm->time_state.td_num); } else { PrintError(vm, VCORE_NONE,"Time dilation specifier in configuration did not" " result in actual time dilation in VM.\n"); } } return 0; } int v3_init_time_vm(struct v3_vm_info * vm) { v3_cfg_tree_t * cfg_tree = vm->cfg_data->cfg; int ret=0; PrintDebug(vm, VCORE_NONE, "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(vm, VCORE_NONE, "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(vm, VCORE_NONE, "Registering TIME_CPUFREQ hypercall.\n"); ret = v3_register_hypercall(vm, TIME_CPUFREQ_HCALL, handle_cpufreq_hcall, NULL); if (ret!=0) { return ret; } PrintDebug(vm, VCORE_NONE, "Registering TIME_RDHTSC hypercall.\n"); ret = v3_register_hypercall(vm, TIME_RDHTSC_HCALL, handle_rdhtsc_hcall, NULL); if (ret!=0) { return ret; } handle_time_configuration(vm, v3_cfg_subtree(cfg_tree, "time")); 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); } static uint32_t gcd ( uint32_t a, uint32_t b ) { uint32_t c; while ( a != 0 ) { c = a; a = b%a; b = c; } return b; } static int compute_core_ratios(struct guest_info * info, uint32_t hostKhz, uint32_t guestKhz) { struct vm_core_time * time_state = &(info->time_state); uint32_t khzGCD; /* Compute these using the GCD() of the guest and host CPU freq. * If the GCD is too small, make it "big enough" */ khzGCD = gcd(hostKhz, guestKhz); if (khzGCD < 1024) khzGCD = 1024; time_state->clock_ratio_num = guestKhz / khzGCD; time_state->clock_ratio_denom = hostKhz / khzGCD; time_state->ipc_ratio_num = 1; time_state->ipc_ratio_denom = 1; return 0; } 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(info->vm_info, info, "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_core_ratios(info, time_state->host_cpu_freq, time_state->guest_cpu_freq); time_state->flags = 0; if (info->vm_info->time_state.flags & V3_TIME_SLAVE_HOST) { time_state->flags |= VM_TIME_SLAVE_HOST; } if (info->vm_info->time_state.flags & V3_TIME_TSC_PASSTHROUGH) { time_state->flags |= VM_TIME_TSC_PASSTHROUGH; } if ((time_state->clock_ratio_denom != 1) || (time_state->clock_ratio_num != 1) || (info->vm_info->time_state.td_num != 1) || (info->vm_info->time_state.td_denom != 1)) { if (time_state->flags | VM_TIME_TSC_PASSTHROUGH) { PrintError(info->vm_info, info, "WARNING: Cannot use reqested passthrough TSC with clock or time modification also requested.\n"); time_state->flags &= ~VM_TIME_TSC_PASSTHROUGH; } time_state->flags |= VM_TIME_TRAP_RDTSC; } PrintDebug(info->vm_info, info, "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); PrintDebug(info->vm_info, info, " td_mult = %d/%d, cl_mult = %u/%u, ipc_mult = %u/%u.\n", info->vm_info->time_state.td_num, info->vm_info->time_state.td_denom, time_state->clock_ratio_num, time_state->clock_ratio_denom, time_state->ipc_ratio_num, time_state->ipc_ratio_denom); PrintDebug(info->vm_info, info, " time source = %s, tsc handling = %s\n", (time_state->flags & VM_TIME_SLAVE_HOST) ? "host" : "none", (time_state->flags & VM_TIME_TSC_PASSTHROUGH) ? "passthrough" : (time_state->flags & VM_TIME_TRAP_RDTSC) ? "trapping" : "offsettting"); time_state->guest_cycles = 0; time_state->tsc_guest_offset = 0; time_state->last_update = 0; time_state->initial_host_time = 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_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; if (*(void**)&time_state->timers) { list_for_each_entry_safe(tmr, tmp, &(time_state->timers), timer_link) { v3_remove_timer(core, tmr); } } }