/* * 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 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 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. */ static int handle_cpufreq_hcall(struct guest_info * info, uint_t hcall_id, void * priv_data) { struct vm_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); PrintDebug("Starting initial guest time as %llu\n", t); info->time_state.last_update = t; info->time_state.initial_time = t; info->yield_start_cycle = t; return 0; } // If the guest is supposed to run slower than the host, yield out until // 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, 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); while (host_time < target_host_time) { v3_yield(info); host_time = v3_get_host_time(time_state); } 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)); 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 0; } int v3_remove_timer(struct guest_info * info, struct vm_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_timer * tmp_timer; uint64_t old_time = info->time_state.last_update; uint64_t cycles; info->time_state.last_update = v3_get_guest_time(&info->time_state); cycles = info->time_state.last_update - old_time; list_for_each_entry(tmp_timer, &(info->time_state.timers), timer_link) { tmp_timer->ops->update_timer(info, cycles, info->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) return ret; info->vm_regs.rcx = info->vm_regs.rax; /* Now do the TSC half of the instruction */ ret = v3_rdtsc(info); if (ret) return ret; return 0; } int v3_handle_rdtscp(struct guest_info * info) { 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_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_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_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; } static int init_vm_time(struct v3_vm_info *vm_info) { int ret; PrintDebug("Installing TSC MSR hook.\n"); ret = v3_hook_msr(vm_info, TSC_MSR, tsc_msr_read_hook, tsc_msr_write_hook, NULL); PrintDebug("Installing TSC_AUX MSR hook.\n"); if (ret) return ret; ret = v3_hook_msr(vm_info, TSC_AUX_MSR, tsc_aux_msr_read_hook, tsc_aux_msr_write_hook, NULL); if (ret) return ret; PrintDebug("Registering TIME_CPUFREQ hypercall.\n"); ret = v3_register_hypercall(vm_info, TIME_CPUFREQ_HCALL, handle_cpufreq_hcall, NULL); return ret; } 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(); 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; time_state->tsc_guest_offset = 0; INIT_LIST_HEAD(&(time_state->timers)); time_state->num_timers = 0; time_state->tsc_aux.lo = 0; time_state->tsc_aux.hi = 0; if (!one_time) { init_vm_time(info->vm_info); one_time = 1; } }