X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=51ac5a76e3a538c91506a3af39ad0cf6c76c3ab5;hb=7229981629c6baa0afb61cc99cfcf6dd029c9c93;hp=781bae70fd86e3fe00b4fcbfee891c6f8f99fcbc;hpb=3676fa947d261206ceff968e4f6b5956900ed277;p=palacios.git diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index 781bae7..51ac5a7 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -41,15 +41,14 @@ * 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. + * 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. * - * 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). @@ -58,7 +57,7 @@ * (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 + * 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. @@ -66,11 +65,17 @@ * 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->guest_cpu_freq; @@ -85,154 +90,89 @@ 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->time_state.vm_enter_host_time = 0; + info->time_state.vm_pause_host_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("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_time * time_state = &(info->time_state); -// PrintDebug("Adding additional offset of %lld to guest time.\n", offset); - time_state->guest_host_offset += offset; + struct vm_core_time * time_state = &(info->time_state); + if (info->vm_info->time_state.follow_host_time) { + PrintError("Cannot offset guest time passage while slaved to host clock.\n"); + return 1; + } else { + time_state->guest_cycles += offset; + } return 0; } -static uint64_t compute_target_host_time(struct guest_info * info) -{ - struct vm_time * time_state = &(info->time_state); - uint64_t guest_elapsed, desired_elapsed; - - guest_elapsed = (v3_get_guest_time(time_state) - 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; - - /* Compute the target host time given how much time has *already* - * passed in the guest */ - target_host_time = compute_target_host_time(info); - - /* 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); - - while (target_host_time > host_time) { - v3_yield(info); - host_time = v3_get_host_time(time_state); +int v3_skip_time(struct guest_info * info) { + if (info->vm_info->time_state.follow_host_time) { + PrintError("Cannot skip guest time passage while slaved to host clock.\n"); + return 1; + } else { + info->time_state.vm_pause_host_time = v3_get_host_time(&info->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 - (sint64_t)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); +static sint64_t host_to_guest_cycles(struct guest_info * info, sint64_t host_cycles) { + return (host_cycles * info->time_state.clock_ratio_num) / info->time_state.clock_ratio_denom; +} + +int v3_time_advance_cycles(struct guest_info * info, uint64_t *host_cycles) +{ + uint64_t t = v3_get_host_time(&info->time_state); + + info->time_state.vm_pause_host_time = t; - if (guest_time < target_guest_time) { - uint64_t max_skew, desired_skew, skew; + if (info->vm_info->time_state.follow_host_time) { + /* How many guest cycles should have elapsed? */ + sint64_t host_elapsed = t - info->time_state.initial_host_time; + sint64_t guest_elapsed = host_to_guest_cycles(info, host_elapsed); - 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 = (guest_time - time_state->enter_time) / 10; + info->time_state.guest_cycles = guest_elapsed; + } else { + uint64_t guest_cycles; + if (*host_cycles) { + guest_cycles = host_to_guest_cycles(info, *host_cycles); } else { - max_skew = 0; + guest_cycles = host_to_guest_cycles(info, (sint64_t)(t - info->time_state.vm_pause_host_time)); } - - desired_skew = target_guest_time - guest_time; - skew = desired_skew > max_skew ? max_skew : desired_skew; - PrintDebug("Guest %llu cycles behind where it should be.\n", - desired_skew); - PrintDebug("Limit on forward skew is %llu. Skewing forward %llu.\n", - max_skew, skew); - - v3_offset_time(info, skew); - } + info->time_state.guest_cycles += guest_cycles; + } return 0; } -// 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) { - - /* 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); - - return 0; +int v3_advance_time(struct guest_info * info) { + return v3_time_advance_cycles(info, NULL); } /* Called immediately upon entry in the the VMM */ int -v3_time_exit_vm( struct guest_info * info ) +v3_time_exit_vm( struct guest_info * info, uint64_t * host_cycles ) { - struct vm_time * time_state = &(info->time_state); - - time_state->exit_time = v3_get_host_time(time_state); - - return 0; + return v3_time_advance_cycles(info, host_cycles); } /* 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 guest_time, host_time; - - guest_time = v3_get_guest_time(time_state); - host_time = v3_get_host_time(time_state); - time_state->enter_time = host_time; - time_state->guest_host_offset = guest_time - host_time; + struct vm_core_time * time_state = &(info->time_state); + uint64_t host_time = v3_get_host_time(&info->time_state); + time_state->vm_enter_host_time = host_time; return 0; } @@ -263,21 +203,26 @@ int v3_remove_timer(struct guest_info * info, struct v3_timer * timer) { } void v3_update_timers(struct guest_info * info) { - struct vm_time *time_state = &info->time_state; + struct vm_core_time *time_state = &info->time_state; struct v3_timer * tmp_timer; - uint64_t old_time = info->time_state.last_update; sint64_t cycles; + uint64_t old_time = time_state->last_update; time_state->last_update = v3_get_guest_time(time_state); - cycles = time_state->last_update - old_time; - V3_ASSERT(cycles >= 0); + cycles = (sint64_t)(time_state->last_update - old_time); + if (cycles < 0) { + PrintError("Cycles appears to have rolled over - old time %lld, current time %lld.\n", + old_time, time_state->last_update); + return; + } - // V3_Print("Updating timers with %lld elapsed cycles.\n", cycles); + PrintDebug("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 @@ -347,7 +292,7 @@ int v3_handle_rdtscp(struct guest_info * info) { 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); + struct vm_core_time * time_state = &(info->time_state); V3_ASSERT(msr_num == TSC_AUX_MSR); @@ -359,7 +304,7 @@ static int tsc_aux_msr_read_hook(struct guest_info *info, uint_t msr_num, 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); + struct vm_core_time * time_state = &(info->time_state); V3_ASSERT(msr_num == TSC_AUX_MSR); @@ -383,14 +328,14 @@ static int tsc_msr_read_hook(struct guest_info *info, uint_t msr_num, 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); + 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; + time_state->tsc_guest_offset = (sint64_t)(new_tsc - guest_time); return 0; } @@ -419,6 +364,13 @@ int v3_init_time_vm(struct v3_vm_info * vm) { ret = v3_register_hypercall(vm, TIME_CPUFREQ_HCALL, handle_cpufreq_hcall, NULL); + vm->time_state.td_num = 1; + vm->time_state.td_denom = 1; + PrintDebug("Setting base time dilation factor to %d/%d.\n", + vm->time_state.td_num, vm->time_state.td_denom); + + vm->time_state.follow_host_time = 1; + PrintDebug("Locking guest time to host time.\n"); return ret; } @@ -430,7 +382,7 @@ void v3_deinit_time_vm(struct v3_vm_info * vm) { } void v3_init_time_core(struct guest_info * info) { - struct vm_time * time_state = &(info->time_state); + struct vm_core_time * time_state = &(info->time_state); v3_cfg_tree_t * cfg_tree = info->core_cfg_data; char * khz = NULL; @@ -450,15 +402,25 @@ void v3_init_time_core(struct guest_info * info) { time_state->guest_cpu_freq = time_state->host_cpu_freq; } + /* Compute these using the GCD() of the guest and host CPU freq. + * If the GCD is too small, make it "big enough" */ + time_state->clock_ratio_num = 1; + time_state->clock_ratio_denom = 1; + 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->guest_cycles = 0; time_state->tsc_guest_offset = 0; + time_state->last_update = 0; + + time_state->initial_host_time = 0; + time_state->vm_enter_host_time = 0; + time_state->vm_pause_host_time = 0; + + time_state->time_flags = 0; // XXX need to set trap TSC flag or not wisely INIT_LIST_HEAD(&(time_state->timers)); time_state->num_timers = 0; @@ -469,7 +431,7 @@ void v3_init_time_core(struct guest_info * info) { void v3_deinit_time_core(struct guest_info * core) { - struct vm_time * time_state = &(core->time_state); + struct vm_core_time * time_state = &(core->time_state); struct v3_timer * tmr = NULL; struct v3_timer * tmp = NULL;