X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?p=palacios.git;a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=dff562b84f3f876a4a8db028573375be5c747026;hp=e7d5cfece6edb99dbea444d5c51b3511c1810afc;hb=88a3605446744969abe6f193a7bc20e62d5aa555;hpb=40e3dd3f222e2638dbdae0eadaf505e1f7a82ecc diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index e7d5cfe..dff562b 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -18,112 +18,157 @@ * redistribute, and modify it as specified in the file "V3VEE_LICENSE". */ -#include #include +#include #include -#ifndef CONFIG_DEBUG_TIME +#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_time * time_state = &(info->time_state); + struct vm_core_time * time_state = &(info->time_state); - info->vm_regs.rbx = time_state->cpu_freq; + info->vm_regs.rbx = time_state->guest_cpu_freq; - PrintDebug("Guest request cpu frequency: return %ld\n", (long)info->vm_regs.rbx); + 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); -void v3_init_time(struct guest_info * info) { - struct vm_time * time_state = &(info->time_state); + // PrintDebug(info->vm_info, info, "Guest request host TSC: return %ld\n", (long)info->vm_regs.rbx); + + return 0; +} - time_state->cpu_freq = V3_CPU_KHZ(); - - time_state->pause_time = 0; - time_state->last_update = 0; - time_state->host_offset = 0; - time_state->offset_sum = 0; - INIT_LIST_HEAD(&(time_state->timers)); - time_state->num_timers = 0; - - v3_register_hypercall(info->vm_info, TIME_CPUFREQ_HCALL, handle_cpufreq_hcall, NULL); -} 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.pause_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(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; } -int v3_pause_time(struct guest_info * info) { - V3_ASSERT(info->time_state.pause_time == 0); - info->time_state.pause_time = v3_get_guest_time(&info->time_state); - PrintDebug("Time paused at guest time as %llu\n", - info->time_state.pause_time); - 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; } -/* Use a control-theoretic approach, specifically a PI control approach, - * to adjust host_offset towards 0. Overall control documentation in - * palacios/docs/time_control.tex Control parameters are P and I, - * broken into rational numbers - */ +/* +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; -/* These numbers need to be actually determined by pole placement work. They're - * just blind guesses for now, which is a really bad idea. :) */ -#define P_NUM 1 -#define P_DENOM 2 -#define I_NUM 1 -#define I_DENOM 20 - -void adjust_time_offset(struct guest_info * info) { - /* Set point for control: Desired offset = 0; - * Error = host_offset - 0 = host_offset */ - - sint64_t adjust; - - /* Update the integral of the errror */ - info->time_state.offset_sum += info->time_state.host_offset; - adjust = (P_NUM * info->time_state.host_offset) / P_DENOM + - (I_NUM * info->time_state.offset_sum) / I_DENOM; - - /* We may want to constrain *adjust* because of - * resolution/accuracy constraints. Explore that later. */ - info->time_state.host_offset -= adjust; - return; -} - -int v3_resume_time(struct guest_info * info) { - uint64_t t = v3_get_host_time(&info->time_state); - V3_ASSERT(info->time_state.pause_time != 0); - info->time_state.host_offset = - (sint64_t)info->time_state.pause_time - (sint64_t)t; -#ifdef CONFIG_TIME_TSC_OFFSET_ADJUST - adjust_time_offset(info); -#endif - info->time_state.pause_time = 0; - PrintDebug("Time resumed paused at guest time as %llu " - "offset %lld from host time.\n", t, info->time_state.host_offset); + cl_num = core_time_state->clock_ratio_num; + cl_denom = core_time_state->clock_ratio_denom; - return 0; + 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)); -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); + 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; @@ -131,11 +176,10 @@ int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops, 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--; @@ -144,14 +188,360 @@ int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) { } 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; + 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; +} + - info->time_state.last_update = v3_get_guest_time(&info->time_state); - cycles = info->time_state.last_update - old_time; +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(tmp_timer, &(info->time_state.timers), timer_link) { - tmp_timer->ops->update_timer(info, cycles, info->time_state.cpu_freq, tmp_timer->private_data); + if (*(void**)&time_state->timers) { + list_for_each_entry_safe(tmr, tmp, &(time_state->timers), timer_link) { + v3_remove_timer(core, tmr); + } } }