X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=2295b3fc90d8ac340ba93eef6dfbbacb10681bf0;hb=8a3dbb70c29175bad79764a0b2f3961b98138bb2;hp=0a719c59b44e674616fa1366d1232bc262ac1bd9;hpb=f9bb3db89469169bb5775dc031d89e570c6fed70;p=palacios.git diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index 0a719c5..2295b3f 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -1,59 +1,492 @@ -/* Northwestern University */ -/* (c) 2008, Jack Lange */ +/* + * 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 "palacios/vmm_time.h" -#include "palacios/vmm.h" +#include +#include +#include +#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 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. + */ - 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_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.enter_time = 0; + info->time_state.exit_time = t; + info->time_state.last_update = t; + info->time_state.initial_time = t; + info->yield_start_cycle = t; + + 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; +} + +#ifdef V3_CONFIG_TIME_DILATION +static uint64_t compute_target_host_time(struct guest_info * info, uint64_t guest_time) +{ + struct vm_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_time * time_state = &(info->time_state); + uint64_t host_elapsed, desired_elapsed; + + 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; + + return time_state->initial_time + desired_elapsed; + +} + +/* 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_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_compute_guest_time(time_state, host_time); + 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_compute_guest_time(time_state, host_time); + + /* 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_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) / 10.0; + } else { + max_skew = 0; + } + + 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; +} + +/* Called immediately upon entry in the the VMM */ +int +v3_time_exit_vm( struct guest_info * info ) +{ + struct vm_time * time_state = &(info->time_state); + + time_state->exit_time = v3_get_host_time(time_state); + + return 0; +} + +/* 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 host_time; + + host_time = v3_get_host_time(time_state); + time_state->enter_time = host_time; +#ifdef V3_CONFIG_TIME_DILATION + { + uint64_t guest_time; + sint64_t offset; + guest_time = v3_compute_guest_time(time_state, host_time); + // XXX we probably want to use an inline function to do these + // time differences to deal with sign and overflow carefully + offset = (sint64_t)guest_time - (sint64_t)host_time; + PrintDebug("v3_time_enter_vm: guest time offset %lld from host time.\n", offset); + time_state->guest_host_offset = offset; + } +#else + time_state->guest_host_offset = 0; +#endif + + 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_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_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); +int v3_handle_rdtscp(struct guest_info * info) { + PrintDebug("Handling virtual RDTSCP call.\n"); - timer->ops = ops; - timer->private_data = private_data; + v3_rdtscp(info); - list_add(&(timer->timer_link), &(info->time_state.timers)); - info->time_state.num_timers++; + info->vm_regs.rax &= 0x00000000ffffffffLL; + info->vm_regs.rcx &= 0x00000000ffffffffLL; + info->vm_regs.rdx &= 0x00000000ffffffffLL; - return 0; + 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); -int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) { - list_del(&(timer->timer_link)); - info->time_state.num_timers--; + msr_val->lo = time_state->tsc_aux.lo; + msr_val->hi = time_state->tsc_aux.hi; - V3_Free(timer); - return 0; + 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; +} + + +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); + + 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_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->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; +} -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_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; }