X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=palacios%2Fsrc%2Fpalacios%2Fvmm_time.c;h=44affe42f5513b2560ca3ae73cda813c7c528fed;hb=07a12ade201ee7c2fe2358084ca079d2facac500;hp=2d5c74ee133632283d391efdc9fa2a475b414b74;hpb=cd3edffa0e451af761b9dcee021ca06ebb301345;p=palacios.git diff --git a/palacios/src/palacios/vmm_time.c b/palacios/src/palacios/vmm_time.c index 2d5c74e..44affe4 100644 --- a/palacios/src/palacios/vmm_time.c +++ b/palacios/src/palacios/vmm_time.c @@ -41,18 +41,31 @@ * 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 as a multipler/offset from (1) above + * 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. */ @@ -81,20 +94,31 @@ int v3_start_time(struct guest_info * info) { // 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) -{ +int v3_adjust_time(struct guest_info * info) { struct vm_time * time_state = &(info->time_state); - uint64_t guest_time, host_time, target_host_time; - guest_time = v3_get_guest_time(time_state); - host_time = v3_get_host_time(time_state); - target_host_time = (host_time - time_state->initial_time) * - time_state->host_cpu_freq / time_state->guest_cpu_freq; - while (host_time < target_host_time) { - v3_yield(info); + 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; } - time_state->guest_host_offset = guest_time - host_time; return 0; } @@ -113,7 +137,6 @@ int v3_add_timer(struct guest_info * info, struct vm_timer_ops * ops, return 0; } - int v3_remove_timer(struct guest_info * info, struct vm_timer * timer) { list_del(&(timer->timer_link)); info->time_state.num_timers--; @@ -135,12 +158,13 @@ void v3_update_timers(struct guest_info * info) { } } - /* * 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 the host TSC. If the guest write's the to TSC, we handle - * this by changing that offset. + * 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) { @@ -170,8 +194,7 @@ int v3_rdtscp(struct guest_info * info) { if (ret) return ret; info->vm_regs.rcx = info->vm_regs.rax; - /* Now do the TSC half of the instruction, which may hit the normal - * TSC hook if it exists */ + /* Now do the TSC half of the instruction */ ret = v3_rdtsc(info); if (ret) return ret; @@ -237,6 +260,7 @@ static int tsc_msr_write_hook(struct guest_info *info, uint_t msr_num, return 0; } + static int init_vm_time(struct v3_vm_info *vm_info) { int ret; @@ -258,11 +282,23 @@ static int init_vm_time(struct v3_vm_info *vm_info) { 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(); - time_state->guest_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; @@ -285,3 +321,6 @@ void v3_init_time(struct guest_info * info) { + + +